extfieldsofstudy: Psychology Medicine

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What matters to infrequent customers: a pragmatic approach to understanding perceived value and intention to revisit trendy coffee café

Notwithstanding the rise of trendy coffee café, little is done to investigate revisit intention towards the café in the context of developing markets. In particular, there is a lack of study which provides theoretical and practical explanation to the perceptions and behaviours of infrequent customers. Hence, the study aims to look into the subject matter by using the theory of reasoned action and social exchange theory as the underpinning basis. The framework proposed by Pine and Gilmore (Strat Leadersh 28:18–23, 2000), which asserts the importance of product quality, service quality and experience quality in a progressive manner, is used to decompose perceived value in the model so as to determine their effects on intention to revisit the café. Given the importance to gain practical insights into revisit intention of infrequent customers, pragmatism stance is assumed. Explanatory sequential mixed-method design is thus adopted whereby qualitative approach is used to confirm and complement quantitative findings. Self-administered questionnaire-based survey is first administered before personal interview is carried out at various cafés. Partial least squares structural equation modelling and content analysis are appropriated successively. In the quantitative findings, although product quality, service quality and experience quality are found to have positive effect on perceived value and revisit intention towards trendy coffee café, experience quality is found to have the greater effect than the others among the infrequent customers. The qualitative findings not only confirm their importance, but most importantly explain the favourable impressions they have at trendy coffee café based on their last in-store experience. While product and service quality might not necessary stimulate them to revisit trendy coffee café, experience quality driven by purposes of visit would likely affect their intention to revisit. As retaining customers is of utmost importance to businesses, and infrequent customers more than often make up the majority of the customers, the study provides meaningful and practical understanding of revisit intention.

Background
Creating customer value has become an essential component that contributes to business competitive advantage (Woodruff 1997). The ability of any businesses to deliver superior value is pivotal to customers' perception towards the quality of their offerings. The added value offered to and appreciated by customers, be it product or service, is believed to have consistently generated favourable behavioural outcomes, such as loyalty, consumption behaviour and repeated visit (Wakefield and Blodgett 1996). Hence, in food and beverage businesses, it is pivotal to know customers' perceptions so as to come out with effective operation designs to stimulate their revisit intention.
Although trendy coffee, such as posh coffee, may have once seemed high-priced, people today consider it as an affordable and even indispensable luxury. Despite being Open Access *Correspondence: hiramparousia@gmail.com 1 Institute of Borneo Studies, Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia Full list of author information is available at the end of the article a developing country with a population of 30 million, Malaysia is one of the emerging markets which shows promising association between Gross Domestic Product per capital and the amount of coffee consumed (International Coffee Council 2014). Since Malaysian coffee market is in the increasing trend, various business organizations are willing to invest in coffee-related businesses. As a result, the growth of retail coffee franchises, such as Starbucks, Coffee Bean & Tea Leaf, Earthlings, and Dômeand, can be seen in Malaysia in the past decade. Trendy coffee café has become one of the fastest growing business in food and beverage industry, and its businesses is estimated to grow more rapidly in the coming years (Agriculture and Agri-Food Canada 2014).
Competitions between trendy coffee cafés and conventional coffee shops are predictably inevitable and intense. It compels the managers to find cutting-edge strategy to improve their overall quality to enhance customers' perception and their repeat consumption in store. In addition to attracting new customers, retaining existing customers becomes as important to business's long term sustainability (Hoekstra et al. 1999). Despite the prospects of trendy coffee café business and the extant of literature on customer behaviour in food and beverage industry, it is somewhat surprising that little study has been done to delve into customer perception and revisit intention towards trendy coffee café in the context of developing markets. Since existing customers are made up by frequent and infrequent ones, past findings pertaining to revisit intention of the latter are apparently lacking. While perceived value generates transactions between providers and recipients, it is relatively unknown if the same can be said about infrequent customers. Hence, this study aims to look into the relationship between perceived value, revisit intention and their antecedents of the infrequent customers towards trendy coffee café in Malaysia. The framework proposed by Pine and Gilmore (2000), which asserts the importance of product quality, service quality and experience quality in a progressive manner, is used as antecedent variables to provide more explanation to perceived value. The theory of reasoned action (TRA) and social exchange theory (SET) are appropriated to provide theoretical basis to postulated relationships in the study. Instead of addressing theoretical gap, mixed-method approach is used to connect the underpinning theories to the context of the study so as to usher in more relevant and pragmatic discussions (Granek and Nakash 2015;Seddon and Scheepers 2011). As such the understanding of revisit intention of infrequent customers towards trendy coffee café in Malaysia would be extended. Managerial implications are highlighted to articulate the practical contribution of the study.

Trendy coffee café
Trendy coffee café, which is also known as coffee house or coffee concept shop, is a place where coffee is served as the main beverage but food and other beverages are also available for consumption. Unlike conventional coffee house and local food court, it is designed to provide customers with a pleasant in-store experience. Even though each trendy coffee café has its own characteristics, they share the concept of quality and comfort (Ganea 2012). As a result, serving the best coffee is not always the only objective to satisfy customers, but also creating a coffeedrinking experience to leave them with good impression (Stark 2013). Wi-Fi connection and seating arrangements are some of the augmented products to stimulate their interest and enhance in-store experience.
The economic and social development in Malaysia as well as the increasing exposure to the western culture has seen the dynamic change of people's values and lifestyles (Verma 2002). Although the quality of coffee, such as its ingredients and taste, used to be the prime reason for dining at a coffee café, other factors have begun to play significant part in their decision making and revisit intention. Notwithstanding a developing country, Malaysian customers are found to be prepared to pay premium price for a cup of coffee when they see additional values in it. Consequently, trendy coffee cafés, especially the retail coffee franchises, have evolved to become not only a dining place, but also a venue for personal leisure and collective socialization. It even becomes a place for teenagers to hangout (de Luca and Pegan 2013). Ever since Starbucks began its maiden business operation in the capital city of Malaysia in late nineties, trendy coffee cafés have grown rapidly and can now be seen in many populated areas, such as shopping complexes, airports, city centres and town areas throughout the country (Balakrishnan et al. 2009).

Perceived value
Perceived value is one of the most important components in marketing and has become a driving factor to behavioural outcomes in marketplace (Hwang and Kandampully 2015). Value conception is closely associated with the perception of quality (Alex and Thomas 2011). Past findings have shown that product quality has quantifiable impact on customer intention (Woodruff 1997;Alex and Thomas 2011;Asmayadi and Hartini 2015). In the same vein, service quality and performance has long been regarded as an important ingredient that business uses to generate favourable expectation and measure satisfaction, thus ushering in locus of value creation (Parasuraman et al. 1988;Chathoth et al. 2014). Moreover, recent studies have also found that customers make transactions not only for functional reasons, but also emotional satisfaction, which includes fun or enjoyment. Such experience is found to have substantial impact on customer behavioural intention (Ali et al. 2015;Yu and Fang 2013).
The framework proposed by Pine and Gilmore (2000) demonstrates the progression of economic value and provides a comprehensive understanding between the capacity of business and customer behaviour. Apart from the offering of products, it reveals the need and importance of progression in stages: from product to service, and from service to experience. The rationale of the framework is that achieving customer expectation with product might not be sufficient for business to create value with customers in contemporary and future markets. Given the fact that trendy coffee cafés offer not only exquisite food and beverages, but also fine services, and pleasant atmosphere which enhance customers' overall experience, it is interesting to know the perception of infrequent customers towards product quality, service quality and experience quality towards trendy coffee cafés, and how such perception affects their perception of value and revisit intention.

Perceived product quality
Quality has been traditionally defined as a zero error rate, and that is the ability to produce a perfect product at the first try (Parasuraman et al. 1985). As far as customer perception is concerned, the superiority of the product is often regarded as the primary assessment of quality. Past studies have come out with various dimensions to define product quality (Madu et al. 1995;Eduardo et al. 2008;Garvin 1984), and contradicting views are nevertheless found. However, product quality can be generally described as the collection of characteristics and features of a product that contribute to its ability to meet or go beyond given requirement (Parasuraman and Grewal 2000;Ngoc and Uyen 2015). Therefore, perceived product quality can be described as the perceived ability of a product to provide satisfaction relative to the alternatives. It is claimed that product offering value for money not only influences customer behaviour at pre-purchase stage but also their satisfaction as well as post-purchase behaviour (Alex and Thomas 2011). This implies that when customers perceive value in the products they buy or consume due to its superior quality, they are willing to pay more for it, visit the store again and even tell others about it.
In light of the aforementioned, the conception of product quality is of relevance to the present study as it refers to customers' perception towards the products offered by trendy coffee cafés, which in turn infers their evaluation on how well the product specification fits the expectation (Jakpar et al. 2012). Since coffee drinks are the main products and their prices are noticeably higher than those offered in conventional eateries, it is interesting to know the effect of perceived product quality on revisit intention towards trendy coffee café in a developing market.

Perceived service quality
Similar to product quality, various descriptions have been given to explain service quality, including the widely adopted SERVQUAL model (Parasuraman et al. 1988). Service quality has been described as a function of differences between customer expectation and business services (Parasuraman et al. 1985). Customers are often found to be judging the quality of service by comparing what they want from the service with what they eventually receive (Gronroos 1983;Lau et al. 2013). Given the practical gap between what customers want and what they receive, service quality is largely accepted as the perception towards service experience (Ryu et al. 2012). The assumption behind this understanding is that customers perceive quality of service based on service performance or what they actually receive from the deliverance. This includes the behaviour of service employees which has been found to have significant effect on purchase behaviour (Abebe 2014). It has become a significant differentiator and the most powerful competitive weapon to business for attaining efficiency and business performance (Bharadwaj et al. 2015).
In any competitive environment, it is evident that a well-designed process of transaction during which service is purveyed and received is pivotal to business performance and customer satisfaction. When service is perceived as of quality, it generates positive word-ofmouth and continuous visit (Ryu et al. 2012). Since services are variable, and they are produced and consumed at the same time, service providers are often found to be under scrutiny (Kotler and Keller 2007). Hence, perceived service quality is adopted in the present study to investigate its relationship with perceived value and revisit intention of infrequent customers towards trendy coffee café.

Perceived experience quality
The overall level of customer satisfaction and the impression a customer has through interacting with a specific product or service are understood as contextual experience (Alex and Thomas 2011). Hence, customer experience can be described as an engaging act of value co-creation between product or service providers and customers (Schmitt 2010). It can further be defined as cognitive and affective assessment in the process of direct and indirect interaction which eventually affects and moulds perception and subsequent behaviours (Meyer et al. 2007;Page and Conell 2006). Albeit related, experience differs from product and service. While a product is a tangible object, and a service is an intangible activity or process, experience is a personal attachment to the service process in the journey with a series of touch point (Johnston and Kong 2010;Poulsson and Kale 2004). This indicates that the creation of customer experience is embedded in the performance of the business ability to personalize specific prerequisite (Mascarenhas et al. 2006). By instilling memorable experience into the customers across various touch points, it reinforces higher level of loyalty and repeat purchase (Stuart 2006).
It is well documented that an effective creation of customer positive experience is essential to constructing customer loyalty, retention, and subsequently financial success (Klaus and Maklan 2012;Lemke et al. 2011). When customers are impressed in their experience, they tend to remember it and repeat their behaviours. As it is known that trendy coffee cafés offer not only products and services, but also cosy and conducive environment to facilitate various activities, such as reading, socializing and group discussions, they create and offer memorable experience for customers as well. Hence, perceived experience quality is also included in the present study to examine its effect on infrequent customers' perception towards value and revisit intention.

Revisit intention
Intention refers to subjective likelihood of performing a behaviour (Ajzen and Fishbein 1980). It is deemed as the direct determinants of the corresponding behaviour. Past research has supported that beliefs and attitudes are precursors of customers' visible response, such as their purchase and repurchase intention (Huang et al. 2004;Wang et al. 2009). In like manner, past studies in food and beverage sector have also indicated that favourable perception and experience, thus overall satisfaction, are important predictors of customer intent to return (Nadiri and Gunay 2013;Oh 2000;Pettijohn et al. 1997;Qu 1997;Weiss et al. 2005). Therefore, intention is often used to better understand how perception can affect subsequent behaviour.
It is well documented that intention to purchase a product is highly related with the product quality (Wells et al. 2011). In other words, customers are willing to pay more if they perceive value in the product (Michaud et al. 2012). However, studies have also suggested the relevance of other influences, such as internal impulse and external environment (Puccinelli et al. 2009). This ushers in the importance of service quality and experience quality. It is no surprise that perceived service quality is also found to affect behavioural intention (Kim and Moon 2009). Service outcomes, such as revisit intention, come from the integration of customers' perceived performance, expectation, and normative evaluation to the physical environment in which a service process takes place (Wakefield and Blodgett 1999). Past studies not only offer evidence that service quality perceptions positively affect behavioural intentions (Zeithaml et al. 1996), they also highlight the effect of experiential value on positive word of mouth and intention to revisit (Nadiri and Gunay 2013). Hence, revisit intention is adopted as the dependent variable or outcome construct in the study.

Frequency of visit
Frequency of visit is found to be associated with perception towards restaurant performance (Kim and Kim 2004). It is also found to be related to loyalty to preferred restaurant and willingness to pay more for the product and service (Clark and Wood 1998). The underlying principle lies with the expectations of quality. The more frequently customers visited the restaurant, the higher their expectation on quality dimensions (Johnson and Mathews 1997). Hence, frequent customers are likely to have higher expectations of product and service quality than infrequent ones as they anticipate the deliverance of quality during their visits (Bornstein 1989). Moreover, frequent customers are described as ones who will place more reliance on information from internal sources, such as their memories, than external sources, such as advertisements and friends' opinions than infrequent ones (Foulkes 1984). However, in a competitive business environment, the perceptions of infrequent customers cannot be overlooked and they might represent the larger segments in the market. Given the exploratory component of this part of the study, the perception of infrequent customers towards product quality, service quality and experience quality, and revisit intention towards trendy coffee café is looked into. Since past literature reviews little to define frequency of visit in the context of trendy coffee café, a preliminary study is conducted to explore and differentiate infrequent customers from the frequent ones.

Theoretical consideration
Two theories are utilized as the basis to postulate the relationships of variables for the present study. Firstly, the theory of reasoned action (TRA), developed by Ajzen and Fishbein (1980), serves as the primary theoretical foundation to investigate the effect of perceived quality on revisit intention towards trendy coffee café. While belief is generally described as specific descriptions of the object's attributes, attitude is defined as a learned predisposition which ushers in response in a consistent manner (Aaker et al. 2001;Fishbein 1967). As such, the perceptions towards product quality, service quality and experience quality are constructed as beliefs towards trendy coffee café, and perceived value as attitude in the study. Since TRA elucidates direct relationship between attitude and behavioural intention, it establishes the basis for the relationship between perceived value and revisit intention.
Secondly, the social exchange theory (SET) is also utilized as supporting basis to the postulated relationships. SET is among the most influential conceptual paradigms for understanding interdependent transactions (Cropanzano and Mitchell 2005). One of the most fundamental tenets is the expectation of reciprocity (Gouldner 1960). It is also known as reciprocal exchange whereby one party's actions are contingent on the other's behaviour (Molm 2003). Once the transaction is in motion, each outcome will create a self-reinforcing cycle. Such transaction is most often studied in workplace relationships (Shore et al. 2004), and marketplace (Houston et al. 1992;De Ruyter and Wetzels 2000). Given the fact that exchange of value is what drives the development of trendy coffee café, SET provides theoretical and practical basis to the reciprocal relationship between perceived qualities and revisit intention of infrequent customers.

Framework and hypotheses
In light of the underlying theories and literature pertaining to perceived product quality, service quality, experience quality, perceived value and revisit intention, a research framework is developed as shown in Fig. 1.
As past studies generally show the positive effect of perceived product quality, service quality and experience quality on perceived value and various behavioural outcomes (Yu and Fang 2013;Pine and Gilmore 2000), positive-directed hypotheses are developed to test the effect of the said perceptions towards trendy coffee café on revisit intention for infrequent customers. The hypotheses are formulated as follows: There is positive effect of perceived product quality on perceived value of infrequent customers towards trendy coffee café. H 2 There is positive effect of perceived service quality on perceived value of infrequent customers towards trendy coffee café. H 3 There is positive effect of perceived experience quality on perceived value of infrequent customers towards trendy coffee café.
H 4 There is positive effect of perceived value on revisit intention of infrequent customers towards trendy coffee café.

Methods
Due to the lack of literature related to perception of infrequent customers towards trendy coffee café in developing markets and also the potential deficiency of quantitative findings in providing more insights into the investigation (Creswell and Clark 2007), mixed-method design, which assumes pragmatism in its philosophical stance, was adopted in the present study (Teddlie and Tashakkori 2009). As shown in Fig. 2, sequential explanatory design is deemed the most appropriate design as it uses qualitative approach to confirm and complement the findings from the quantitative study (Venkatesh et al. 2013). The combination or "mix" of two approaches would be able to offer more pragmatic and meaningful findings and discussions, thus be of better relevance to the context of the study (Granek and Nakash 2015). A preliminary study using qualitative interview was necessary prior to the main investigation to define infrequent customers based on frequency and purpose of visit. The interview was conducted at the trendy coffee cafés, such as Starbucks and Coffee Beans, rather than  anywhere else for two reasons. Firstly, the target respondents had to be customers of any trendy coffee café. Secondly, it was more practical to interview them at the natural setting to find out why they visited trendy coffee café infrequently (Marshall 1996). As such, it is evident that purposive sampling technique was most suited to sample the respondents for the purpose of the study (Onwuegbuzie and Collins 2007). Thirty customers were approached and asked about their frequency and purpose of visit to trendy coffee cafés and sixteen of them were found to be infrequent customers. Hence, frequency of visit was included in the quantitative study as qualifying question so as to set apart the infrequent customers from the frequent ones in the dataset. In the quantitative stage, self-administered questionnaire was used. In addition to questions about respondents' demographic characteristics, all statements related to perceived product quality, service quality, experience quality, perceived value and revisit intention were adapted from past studies (Yu and Fang 2013;Pine and Gilmore 2000). Multiple statements were used to facilitate reliability and validity check in measurement analysis. A seven-point Likert scale was used, where 1 indicates strongly disagree to 7 indicates strongly agree in the questionnaire. After content validity was ascertained by a marketing professor, a pre-test via debriefing method was administered on three individuals to determine the usability and comprehensibility of the questionnaire so as to eliminate potential problems associated with the wordings, instructions and questionnaire design (Bazera 1996;Hunt et al. 1982).
Using purposive sampling technique, 350 copies of questionnaire were distributed at trendy coffee cafés in Malaysia. 250 usable copies were subsequently collected on the spot, with the acceptable response rate at 71 percent (Richardson 2005;Nulty 2008). Statistical Package for Social Sciences (SPSS) was then used for data entry and cleaning purpose. After setting apart data from frequent customers and removing influential outliers and cases with serious missing values, 162 cases were retained in the dataset for data analysis using structural equation modelling (SEM). The sample size was deemed adequate as it was able to detect medium effect size at a statistical power of 80 % using power analysis (Cohen 1988;Hair et al. 2014). Since the emphasis of the study is on prediction, structural equation modelling of partial least squares (PLS-SEM), which is a variance-based SEM, is regarded more appropriate in analysis (Hair et al. 2014).
Once the quantitative findings were obtained, an interview protocol was designed accordingly. The purpose was to find out why infrequent customers would or would not revisit trendy coffee café. Semi-structured interview was administered to allow probes so as to elicit more detailed information pertaining to perceived quality, value and revisit intention from the customers on the basis of data richness (Tong et al. 2007). Fifteen interviews were predetermined with reference to past literature (Guest et al. 2006), and like the preliminary study, they were conducted at various trendy coffee cafés. This was to ensure that all sampled respondents were the actual customers and they could justify their responses with subjective experiences. All interviews were audio-recorded, transcribed and analyzed using content analysis (Kurasaki 2000). Utilizing inter-coder agreement in analysis, data saturation was achieved in the tenth transcript (Carey et al. 1996;Morse 1995). Given the purpose of sequential explanatory mixed-method design, the qualitative findings would then be useful to confirm and complement the quantitative findings pertaining to revisit intention towards trendy coffee café (Onwuegbuzie and Collins 2007).

Preliminary study
In the preliminary study, the interview findings show that the infrequent customers are those who seldom visit trendy coffee café. Either they visit the café not more than once a month or when there is a specific purpose for them to be there. Generally, they neither take the initiative to visit nor suggest to having coffee at trendy coffee café. More than often they are asked to meet up friends there or they need a place to rest, such as at the airport or shopping complex.

Quantitative stage
As sequential explanatory mixed-methods design is adopted, the findings are presented in quantitative stage and qualitative stage. Out of the 162 respondents, the numbers of male and female respondents are about equal. Malay and Chinese respondents make up the majority of the sample as they are the two most populous ethnic groups in Malaysia, and they are more likely to visit trendy coffee cafés which are located in urban areas. Moreover, 110 respondents who are aged 21-25 are found in the sample, showing the popularity of the café among university students and young adults.

Measurement model
Before moving into hypothesis testing, construct validity was first determined. Table 1 indicates the assessment of reliability and validity in the data of the study. The composite reliability (CR) and Cronbach alpha values of more than 0.70 demonstrate that these constructs possess adequate level of internal consistency (Gefen et al. 2000). Similarly, the constructs under investigation demonstrate good convergent validity as they all achieve the minimum threshold value of 0.5 for average variance extracted (AVE) (Bagozzi and Yi 1988). It explains that the items explain more than 50 % of the construct's variances (Hair et al. 2014). Hence, no item was removed from the observation.
Assessment of discriminant validity using Henseler et al. 's heterotrait-monotrait (HTMT) ratio of correlations (2015) criterion is determined as shown in Table 2. Since the correlation values corresponding to the respective constructs do not violate HTMT.90 criterion (Henseler et al. 2015), it is suffice to conclude that construct validity is established in the measurement model.

Structural model
Before performing latent variable analysis in structural model, it is important to ensure that there are no collinearity issues between the constructs under investigation. Table 3 presents that the variance inflation factor (VIF) value for each construct is lower than the offending value of 3.3 (Diamantopoulos and Siguaw 2006). Hence, it suggests that collinearity is of no concern in the study.
In order to test the hypotheses, bootstrapping procedure is used to generate results for each path relationship in the model as shown in Table 4. Bootstrap sub-samples with 5000 cases are created to allow the procedure to estimate the model for each subsample (Hair et al. 2014). All path relationships are found to be significant at 99 and 95 % confidence interval (PROD → VAL, ß = 0.226, p < 0.01; SERV → VAL, ß = 0.201, p < 0.05; EXP → VAL, ß = 0.394, p < 0.01; VAL → INT, ß = 0.623, p < 0.01). Given that all have positive relationship, it is surmised that the four hypotheses in the study are supported.
Despite having decisions for the hypotheses, findings of co-efficient of determination (R 2 ), the effect size (f 2 ), as well as the cross-validated redundancy (Q 2 ) of exogenous constructs on endogenous constructs are also presented as shown in Table 5. The values for co-efficient of determination (R 2 ) of 0.388 and 0.523 suggest that the exogenous variables in this study explain 38.8 % of variances in perceived value and 52.3 % of variances in revisit intention; an indication of substantial explanatory capacity (Cohen 1988). Since the focus of PLS-SEM is on prediction, blindfolding procedure is used (Chin 1998). The Q 2      (Fornell and Cha 1994).
Notwithstanding significant, f 2 values disclose the importance of each exogenous construct to endogenous constructs. It is interesting that effect of perceived experience quality on perceived value (EXP, f 2 = 0.157) is larger than that of perceived product quality and service quality(PROD, f 2 = 0.058; SERV, f 2 = 0.036) for infrequent customers. Evidently, perceived value has large effect on revisit intention towards trendy coffee café (VAL, f 2 = 0.633).

Qualitative stage
Apart from questions pertaining to purposes or reasons to visit trendy coffee café, it has become necessary to find out if infrequent customers are indeed appreciating experience quality more than product and service quality, thus making them willing to revisit. The responses elicited from interviews not only confirm the role of perceived product quality, service quality and experience quality, they also complement the findings on the magnitude of experience quality as shown in Table 6.
In spite of being infrequent customers, the findings show that they believe there is generally good quality in the product and service offered at the trendy coffee café, and they also have had good in-store experience. Even though they think the products are expensive, and the coffee does not necessarily taste better than that of the local coffee shops, they accept that the products are usually good. In like manner, the overall perception about the service quality and performance is also positive. Note worthily, some do not think the staffs are actually doing much. The aforementioned could well explain why the effect size of the relationship between perceived product quality and perceived value, as well as the relationship between perceived service quality and perceived value is found to be minimal. This infers that product quality and service quality at trendy coffee café contribute little to their revisit intention. In other words, infrequent customers would not visit trendy coffee café because of the craving for coffee and the services.
Nevertheless, the findings show the magnitude of experience quality in value perception and revisit intention. Although they rarely consume coffee there, they have fond memory about their last in-store experience. Having good impressions and taking the venue of trendy coffee café into consideration for a specific purpose, such as meeting friends or having discussions there, justify why perceived experience quality carries the most effect on perceived value as shown in quantitative findings. Hence, it can be concluded that the experience quality of infrequent customers at trendy coffee café is mainly constituted by the impressions they have based on their previous visits and their attachment in various contact points. Infrequent customers are not there mainly for the product or service, rather they are there and might visit again for specific purposes which they have experienced before.

Implications and conclusion
This study has provided some empirical insights into the revisit intention of infrequent customers towards trendy coffee café in a developing market with theoretical foundation. Both quantitative and qualitative findings support the notions that revisit intention towards trendy coffee café is affected by perceived value, which, in turn, is predicted by perceived product quality, service quality and experience quality. The findings also support what Pine and Gilmore (2000) advocate about the progression of economic value whereby experience quality is believed to be the cutting edge approach in contemporary market. In general, it is understood that experience quality helps augment the product or service, thus reinforcing customer's revisit intention towards product or service providers (Clark and Wood 1998;Walls et al. 2011). It certainly holds true for infrequent customers as found in the present study.
In light of the findings, it is imperative that managers of trendy coffee café come out with comprehensive business strategies and practices to exemplify in-store experience quality so as to stimulate the interest of existing customers who visit the café infrequently. Over-emphasizing on product quality and frequent customers would likely lead to marketing myopia (Smith et al. 2010). The numbers of frequent and infrequent customers sampled in quantitative stage imply the latter belongs to the majority; and this could well reflect the actual situations of most food and beverage sectors in developing markets. As these markets are emerging as lucrative business regions, the managers cannot afford to lose infrequent ones. Therefore, the contemporary challenge is about keeping existing customers, and converting the infrequent ones to frequent ones by rewarding them with memorable experience when they are at the café.
The pragmatic approach using mixed-method design has indeed elucidated reasons behind the phenomenon under investigation. Such approach is gaining popularity due to its usefulness in providing meaningful and practical interpretations of findings (Granek and Nakash 2015). There are, however, caveats to the study which are worth investigating. Firstly, as different segments are more likely to have different perceptions (Clark and Wood 1998), the sample of the study, which is predominantly made up by university students and young adults, might have come short in extrapolating the findings to wider populations. From the perspectives of developing and multi-cultural country like Malaysia, factors, such as income level, generations and ethnicity, could prove to be vital in divulging more insights about revisit intention towards trendy coffee café. Secondly, the unclassified findings in qualitative stage also suggest that there are more to revisit intention towards trendy coffee café than perceptions about value and about product, service and experience quality. It is worth noting that normative influence could be crucial to improving revisit intention of infrequent customers. Thirdly, the re-specification of perceived value as mediator and the inclusion of moderators and multiple outcome variables could well extend TRA and SET, and thus provide more holistic understanding to revisit intention towards trendy coffee café.


extfieldsofstudy:
Engineering
Computer Science
Physics

text:
On the Spectral Efficiency Limits of an OAM-based Multiplexing Scheme

As reported in several recent publications, a spatial multiplexing involving the transmission of orthogonal waves carrying Orbital Angular Momentum (OAM) is unable to provide spectral efficiency improvements with respect to the conventional techniques. In this work we emphasize how the limits of an OAM multiple transmission between antenna arrays can be derived from the Shannon capacity formula, taking as a reference the performance of a multiplexing method based on the higher-order channel modes. Our approach clearly indicates that the two techniques offer the same on-axis performance. Conversely, small misalignments in the arrays positions affect the OAM scheme, highlighting the greater robustness of a traditional multiplexing method in the context of radio communications.

On the Spectral Efficiency Limits of an OAM-based Multiplexing Scheme Andrea Cagliero and Rossella Gaffoglio
Abstract-As reported in several recent publications, a spatial multiplexing involving the transmission of orthogonal waves carrying Orbital Angular Momentum (OAM) is unable to provide improvements in spectral efficiency with respect to the conventional techniques. With this work we want to emphasize how such consideration can be easily derived from the Shannon capacity formula. Taking as a reference the performance of a multiplexing scheme based on the higher-order channel singular modes, we analyze the spectral efficiency of an OAM multi-mode transmission between antenna arrays. Our approach clearly indicates that the two techniques offer the same on-axis performance. Conversely, small misalignments in the arrays positions strongly affect the OAM scheme, highlighting the greater robustness of a traditional multiplexing method in the context of radio communications.

I. INTRODUCTION
A S a result of the growing spread of broadband services, the recent years have witnessed a strong increase in the demand for spectral resources within the context of wireless communications. To address this problem, the technological evolution in telecommunications has led to the development of new techniques employing different modulation schemes, polarization and spatial/temporal diversity in order to exploit the electromagnetic spectrum more efficiently. In addition to the above mentioned methods, it has been recently proposed a new approach based on the use of waves carrying Orbital Angular Momentum (OAM), with relevant applications both in optics [1]- [3] and at the radio frequencies [4]- [6].
OAM beams are well-known solutions to the Helmholtz equation, characterized by the presence of a phase singularity along the propagation axis, which determines a central intensity null and twisted wavefronts. Mathematically, such phase structure is described by a screw dislocation of the form e i ϕ , where ϕ is the azimuthal angle, while the index ∈ Z, related to the orbital angular momentum content of the beam, indicates the number of twists performed by the phase profile around the central point of zero intensity [7].
The orthogonality among OAM modes with different index led to consider the possibility of exploiting the peculiar phase distribution of such beams for conveying multiple communication subchannels at the same frequency [5], [6]. Although this idea sounds innovative from a physical point of view, it has been shown that an OAM-based transmission can be considered as a particular case of spatial multiplexing A. Cagliero and R. Gaffoglio are with the Department of Physics, University of Torino, I-10125 Torino, Italy (e-mail: andrea.cagliero@unito.it; rossella.gaffoglio@unito.it).
[8]- [10]. Within this framework, the over-quadratic power decay in the central region has been pointed out as the real drawback to the use of OAM beams [11]; however, it should be noted that such behaviour also affects all the higher-order freespace modes which are generally used in spatial multiplexing. Rather, a more relevant issue lies in the strong sensitivity of the OAM orthogonality to misalignments, which seems to restrict this kind of transmissions to the on-axis line-of-sight (LOS) communications only.
In this letter we provide an in-depth analysis on the limits of OAM radio transmissions by proposing a fair comparison between two multiplexing techniques, one based on OAM modes with index = 0 (OAM Mux) and the other on the channel higher-order singular modes (CM Mux). In a scenario involving antenna arrays, the Shannon spectral efficiency is computed in the two cases as a function of the propagation distance for both on-axis and off-axis configurations; then, a more realistic example is implemented with the use of some commonly employed modulation schemes and the corresponding C/N reference values under Gaussian channel assumption.

II. CHANNEL MATRIX
Let's consider a communication link made of two facing antenna arrays. For an incident electromagnetic beam generated by N T transmitting antennas, the circuit voltage induced on a pth receiving element can be expressed by [12]: where: represents the electric field evaluated at the spatial location of the pth antenna. In the above expressions, k = 2π/λ is the modulus of the wave vector, being λ the wavelength, η is the vacuum impedance, R is the resistance of the radiators and V T n = V 0 ξ T n is the voltage supply relative to the nth transmitting antenna, being ξ T ∈ C N T a unity-normalized vector of input coefficients and V 0 a voltage constant term associated to the input power P in through the following expression:   are the effective heights for each reciprocal link, evaluated in the reference frame of the nth transmitter and the pth receiver, respectively, while w p is the noise contribution. For simplicity, mutual couplings have been neglected. Assuming that the receiving array has N R elements, with reference to expression (1) the input/output relationship for the considered MIMO system can be written as follows: being the receiver noise vector and H ∈ C N R ×N T the channel matrix with elements: By making use of (5), the total power intercepted by the receiving array in the absence of noise can be defined as: where the coefficients ξ R p belong to a unitary-normalized vector ξ R ∈ C N R of ideal beamforming weights introduced at the receiver.
To find the transmit and receive vectors ξ T and ξ R defining the channel modes of a communication system, it is necessary to resort to the singular value decomposition (SVD) of the channel matrix, given by: where U ∈ C N R ×N R and V ∈ C N T ×N T are the unitary matrices containing the left and right singular vectors of H, respectively, while Σ ∈ C N R ×N T is a rectangular diagonal matrix whose elements are the singular values of H arranged by decreasing magnitude. The diagonal entries Σ ii determine the gains of the independent subchannels identified by the coefficients ξ T n = V ni and ξ R p = U * pi . Fig. 1 shows a communication link consisting of a couple of facing uniform circular arrays (UCAs) made of eight crossed half-wave dipoles. The intensity and phase electric field profiles of the first three circularly polarized channel modes relative to the considered system are displayed in Fig.  2 for a frequency f = 584 MHz in the UHF band and a radius R = 1 m for both the arrays.

III. OAM MODES
In the radio domain, OAM beams can be generated by means of an array synthesis process. Starting from given requirements on the array structure, this method allows to find the elements excitations that best reproduce a certain electromagnetic field by solving a linear inverse problem.
Among all the possible array geometries, the most natural layout for the production of OAM radiation with index T is that of a N -element UCA with N > 2| T | [13], which exploits the beams circular symmetry minimizing the number of employed antennas. In this case the input excitations are simply given by: Figure 4. Shannon spectral efficiency for two different multiplexing/demultiplexing methods as a function of the link distance between the facing UCAs of Fig. 1, in the absence of misalignments and for a total input power of 1 kW. The inset shows the critical distance at which the singlechannel transmission of the fundamental = 0 mode (Std case) outperforms the multiplexing methods as a function of the total input power. so that the phase difference between each couple of subsequent elements results 2π T /N .
When considering a communication channel made of two facing UCAs, the helical phase structure of the incoming OAM beam must be properly compensated in order to avoid a null on-axis power transfer response. To this end, by exploiting the reciprocity theorem and the intrinsic orthogonality of OAM beams, the receiving weight coefficients: that must be applied to a N -element receiving UCA in order to maximize the on-axis reception, are obtained by imposing R = T [14]. Fig. 3 shows the intensity and phase electric field profiles of some OAM modes with different index, generated by the transmitting array of Fig. 1 at f = 584 MHz and R = 1 m. It should be noted that the choice of considering circularly polarized crossed dipoles ensures the circular symmetry and thus the OAM orthogonality to be fully preserved.

IV. SHANNON CAPACITY CURVES
Making use of the Shannon capacity formula [15], the total spectral efficiency associated to a mode-division multiplexed transmission over a band-limited Gaussian channel can be expressed by: where Q indicates the number of transmitted modes, P ii out is the properly received power relative to the ith subchannel, N 0 is the thermal Gaussian noise in the considered bandwidth, while P ji out are noise power contributions representing the Figure 5. Shannon spectral efficiency for two different multiplexing/demultiplexing methods as a function of the link distance, when the total input power is fixed at 1 kW. In this case the receiving array of Fig. 1 is rotated by 2 degrees around the y-axis passing through its center. crosstalk among the different modes. As a result, each power ratio in (10) can be intended as the signal-to-interference-plusnoise ratio (SINR) of the ith subchannel.
In order to provide a comparison in terms of spectral efficiency between two different multiplexing schemes, we considered as a common framework the LOS link depicted in Fig. 1 and we set the total input power to a fixed value. Then we evaluated the total spectral efficiency (10) relative to the simultaneous transmission of the second and the third channel modes (CM Mux), on one hand, and of two OAM beams with index = ±1 (OAM Mux), on the other, as a function of the link distance. The total input power has been equally divided in both cases between the two considered subchannels and the power contributions P out have been estimated from (6) by means of the MATLAB R software [16]. Given the ith subchannel, P ii out in (10) represents the power associated to a mode-matched reception, while the P ji out noise contribution provides the intercepted power from the transmitted mode j = i (or T = R in the OAM case), which is negligible only in the absence of misalignments for the modes orthogonality. As we can see from Fig. 4, the two multiplexing methods show the same performance in the on-axis case, i.e., when the arrays are facing each other perfectly. Conversely, as shown in Fig. 5, when a small angular shift in the arrays position is introduced, the CM Mux strongly outperforms the OAM-based scheme, highlighting the greater sensitivity to misalignments of the latter method. It should be noted that in both the reported figures the considered arrays have a radius R = 1 m, the emitted radiation is circularly polarized and the frequency is fixed at 584 MHz with a channel bandwidth of 7.61 MHz. Moreover, it is important to emphasize that, even in presence of misalignments, the beamforming coefficients used to determine the P out contributions in the CM Mux case descend from the SVD of the channel matrix relative to the perfectly aligned arrays, ensuring a fair comparison between the two multiplexing methods.

V. MODULATION SCHEMES
The Shannon capacity formula (10) represents the theoretical tightest upper limit on the spectral efficiency and has little to do with the values actually reachable by the current modulation schemes. In order to make the above analysis more realistic, we compared algorithmically the SINR of each subchannel at various link distances with the minimum required C/N values for some of the most commonly used modulation schemes, from QPSK 1/2 to 4096-QAM 9/10 [17], [18], under the assumption of a Gaussian channel. This allowed us to provide, for all the different subchannels, an estimation of the maximum distances at which each modulation scheme could be employed, with the corresponding spectral efficiency. Since the transmitted modes are supposed to be independently modulated, the global contribution for the multiple channel is simply given by the sum of all the spectral efficiencies relative to each subchannel. In Fig. 6 the obtained spectral efficiency values are hierarchically organized as a function of the corresponding link distances for an off-axis configuration, showing a trend which is found just below the theoretical Shannon curve, as expected. It should be noted that the curve saturation and the sudden drop at small and large distances, respectively, are due to the bounds chosen for the set of modulation schemes.
Even in this simplified study, the CM Mux proves more robust with respect to misalignments, at least within a certain distance which is related to the total input power. Since the two multiplexing methods show the same performance in the on-axis case, the corresponding plot is not reported here for brevity.

VI. CONCLUSIONS
The spectral efficiency of a communication link between two UCAs composed by crossed dipoles has been studied. The performance of the OAM-based multiplexing has been compared with that of a scheme exploiting the first two higher order singular modes of the considered channel. We have proven how the latter method shows a better behaviour in the presence of misalignments, while the two techniques share the same performance in the on-axis configuration. Our results clearly demonstrate that, apart from the simplicity of the generating methods, no benefit can be expected from the use of the OAM-based multiplexing in the considered LOS scenario.

VII. ACKNOWLEDGMENTS
We would like to express our deep gratitude to Alberto Morello, Bruno Sacco and Assunta De Vita, from the Centre for Research and Technological Innovation, RAI Radiotelevisione Italiana, for proposing the main ideas behind this work and to Prof. Giuseppe Vecchi, from the Polytechnic University of Torino, for all the precious teachings.


Temporary contracts: effect on job satisfaction and personal lives of recent PhD graduates

In this study, we assess the effects of temporary employment on job satisfaction and the personal lives of recent PhD graduates. Temporary employment is becoming increasingly prevalent in many sectors, but has been relatively common in academia, especially for early career scientists. Labor market theory shows temporary employment to have a conspicuous negative influence on the job satisfaction and well-being of employees, but also identifies groups that may be exempt from these negative influences, such as the highly educated. Here, we study the effect of temporary employment on the highest educated group in the labor force, PhD graduates. We present findings of a survey of 1133 respondents who obtained their PhD from one of five Dutch universities between 2008 and 2012. Compared to PhDs employed on a permanent contract, PhDs on a temporary contract are less satisfied with their terms of employment, especially if they have no prospect of permanence. Temporary contracts with no prospect of permanence also decrease satisfaction with job content. Conversely, self-employment increases satisfaction with job content. Educational level required for the job also influences job satisfaction to a large degree: working below PhD level negatively affects job satisfaction. Finally, the type of contract affects different aspects of the personal lives of PhDs, such as the ability to obtain a mortgage, the stability of family life, and the possibility to start a family. In conclusion, we show that the highest educated, i.e., PhD graduates are not exempt from the negative influences of temporary employment.

Abstract In this study, we assess the effects of temporary employment on job satisfaction and the personal lives of recent PhD graduates. Temporary employment is becoming increasingly prevalent in many sectors, but has been relatively common in academia, especially for early career scientists. Labor market theory shows temporary employment to have a conspicuous negative influence on the job satisfaction and well-being of employees, but also identifies groups that may be exempt from these negative influences, such as the highly educated. Here, we study the effect of temporary employment on the highest educated group in the labor force, PhD graduates. We present findings of a survey of 1133 respondents who obtained their PhD from one of five Dutch universities between 2008 and 2012. Compared to PhDs employed on a permanent contract, PhDs on a temporary contract are less satisfied with their terms of employment, especially if they have no prospect of permanence. Temporary contracts with no prospect of permanence also decrease satisfaction with job content. Conversely, self-employment increases satisfaction with job content. Educational level required for the job also influences job satisfaction to a large degree: working below PhD level negatively affects job satisfaction. Finally, the type of contract affects different aspects of the personal lives of PhDs, such as the ability to obtain a mortgage, the stability of family life, and the possibility to start a family. In conclusion, we show that the highest educated, i.e., PhD graduates are not exempt from the negative influences of temporary employment.
Electronic supplementary material The online version of this article (doi:10.1007/s10734-016-0050-8) contains supplementary material, which is available to authorized users.

Introduction
Temporary (or fixed-term) employment is becoming a reality for an increasing share of academic researchers. The increase in temporary contracts for academics is especially pronounced for early career researchers and can be observed in many countries, such as the United States (Schuster and Finkelstein 2006: 194), Germany (Waaijer 2015) and the Netherlands (Association of Dutch Universities 2016). However, this shift from permanent to temporary employment is not confined to academia, but applies to all employment sectors. For example, in the Netherlands about half of all recent university graduates are employed on a temporary contract (Bertrand-Cloodt et al. 2012;Statistics Netherlands 2014). Still, in academia temporary employment is even more prevalent than in other sectors, which is easily exemplified by looking at the employment of PhD graduates who have just received their PhD: two-thirds of PhD graduates working outside academia have a permanent job, compared to only one-third for those working in academia (Sonneveld et al. 2010).
The prevalence of temporary employment in academia compared to other sectors raises the question what its effects are on early career researchers. In this study, we study: 1. What is the effect of temporary employment on the job satisfaction of recent PhD graduates? 2. What is the effect of type of employment on the personal life of recent PhDs?
Recent PhDs make for an interesting group to study this effect as we expect a relatively large dichotomization in type of employment by sector. In addition, the fact that the group consists of both permanently and temporarily employed persons makes it possible to estimate the effect of temporary employment using a ''control'' group of permanently employed persons. This is not possible using a group of postdoctoral researchers, for example, as most of these will be employed on a temporary contract. Furthermore, PhDs are an interesting group because they are the highest educated persons in the labor force. Whereas the effects of temporary employment on the labor force as a whole have been relatively well-studied, this is less the case for the highly educated, and not at all for PhDs.
The remainder of the paper is structured as follows. In a review of the literature, we will first provide several theories on the effects of temporary employment, coming from labor market, organization and career literature. Special attention will be given to the national context of the study. Furthermore, we will discuss literature on job satisfaction, focusing on previous studies on job satisfaction among PhDs and factors that influence their job satisfaction. In the methodology section we will describe how the survey has been conducted and which variables were measured. The results and discussion section starts by providing data on the prevalence of different types of temporary employment among the respondents. Then, we will show a comparison of several aspects of job satisfaction by type of employment. As a next step, we determine the effect of temporary employment on job satisfaction while controlling for other factors that may influence it. Finally, we show how type of employment affects the personal lives of recent PhD graduates. In our conclusions section we put our results into the context of the labor market and career literature, and describe the policy implications of our study.

Literature review Temporary employment
In their human resource management, organizations must decide on a strategy regarding the contractual arrangements and thereby the employment relationships with their employees. Most organizations have a core workforce of employees on permanent contracts, supplemented by a flexible supply of temporary workers (Aldrich and Ruef 2006: 97). Having a small core workforce offers the flexibility to adapt to changes in the economic environment, e.g., by reducing the workforce when demand decreases or by adapting the workforce to meet changed skill requirements, without the costs of redundancy pay (Bertrand-Cloodt et al. 2012;Cörvers et al. 2012). At the same time, temporary employees are less likely to be committed to the organization and the knowledge temporary employees obtained is lost when they find employment elsewhere (Aldrich and Ruef 2006: 97). Having a larger core workforce counteracts these issues. In conclusion, there is a tradeoff between the long term (commitment and obtained knowledge) and the short term (flexibility) in contractual arrangement strategies.
In case of universities and public research organizations, these considerations do not apply at the institutional level: their budgets are not heavily determined by market forces and are fairly stable. This is true even in cases where a considerable share of funding is obtained from competitive funding: the sources of competitive funding are themselves fairly stable, and the shares of individual research organizations competing for competitive funding sources are also relatively stable. However, at the level of departments and institutes within the organization, funding levels are more unstable and there the organizational and economic arguments mentioned above might apply. In addition, the acting management of the organizations may apply these considerations to their employees, in order to avoid risks of conflicts within the organization. This could be a reason for the large share of temporary employees modern research organizations, but this mechanism has not been studied in great detail. From work by one of us it appears that this large share has developed mainly as a consequence of the end of the large (budgetary) expansion of the higher education system as a whole (Waaijer 2015).
For workers, too, temporary employment may have two faces. On the one hand, according to dual labor market theory temporary jobs may be considered as low quality or even ''bad'' jobs with low pay and no access to benefits (Kalleberg et al. 2000), from which it is difficult to find a high quality job due to labor market segmentation (e.g., Reich et al. 1973). These bad jobs do not only have poorer terms of employment than permanent jobs, but also have poorer job content, e.g., featuring more monotonous tasks, less opportunity to learn new things and less often being sufficiently demanding (Letourneux 1998). Still, temporary jobs may be preferable to unemployment and can provide a ''stepping stone'' to a permanent job, especially for university graduates (Bertrand-Cloodt et al. 2012).
On the other hand, another body of literature on careers postulates temporary employment to enable ''boundaryless careers'', in which workers do not work in one organization throughout their working life, but rather change employers more often and develop themselves as they wish (Arthur and Rousseau 1996). Following this theory, Marler et al. (2002) distinguish ''boundaryless'' and ''traditional'' temporary employees and find that the boundaryless employees, who prefer temporary jobs, have a higher skill level and experience. Combining both the ''stepping stone'' and ''boundaryless'' theories of temporary employment, temporary jobs may not be ''bad'' jobs for PhD graduates, who are the highest educated group on the labor market.
A reason for this may lie in the psychological contracts formed between employers and employees. A psychological contract is defined as ''individual beliefs, shaped by the organization, regarding terms of an exchange between individuals and their organization'' (Rousseau 1995: 9). If the individual believes the terms of exchange have been breached, the psychological contract is violated. This leads to increased turnover and a decrease in trust and satisfaction in an employment context (Robinson and Rousseau 1994). Using the stepping stone analogy, young, highly educated employees on a temporary contract could experience a balanced exchange between themselves and the employer: employees offer (temporary) labor to the employer, and in turn gain job experience, which they can use in another job. In this case, temporary employment does not necessarily lead to decreased job satisfaction. Indeed, a recent study by Lam and de Campos (2015) found that young scientists involved in so-called collaborative research experienced a balanced psychological contract with their professor or employer and remained invested in their current job, despite the fact that some of them seemed trapped in perennial temporary employment. On the other hand, Thunnissen (2015) described the human resources policy at Dutch universities as an unbalanced situation, in which the long spells of temporary employment for scientists led to dissatisfaction. In this study, we can test whether temporary employment affects recent PhDs.
The national context: temporary employment in the Netherlands As already indicated in our introduction, the past years have seen a large increase in temporary employment in the Netherlands (Bierings et al. 2015). There have been increases in the share of employees with a temporary contract, in the share of self-employed persons without employees (zelfstandige zonder personeel or zzp'er) and in the share of self-employed persons with employees. By 2013, the Netherlands ranked third among the EU-15 countries regarding the share of employees with a temporary contract, after Spain and Portugal (Kösters and Smits 2015). An explanation for a large share of temporary employees is high levels of legal protection against dismissal-in countries where the legal protection against individual dismissal is high, organizations achieve labor flexibility by hiring employees on a temporary contract (Kösters and Smits 2015). When the difference in legal protection of permanent and temporary employees is smaller, the share of temporary employees is often smaller.
In response to the increasing shares of temporary employees, the Netherlands adopted a new law regarding temporary employment, which became effective on 1 July 2015 (Wet werk en zekerheid 2015). In this law, dismissals were simplified by reducing the number of possible legal procedures. At the same time, employees gained the right to compensation if the employer fired them or if they had been employed for over 2 years. In addition, the maximum number of years on a temporary contract was reduced from three to two (with an exception for universities, for whom this period is 4 years). After this period, employees should be employed on a permanent contract. In addition, employees can only be employed on three temporary contracts (both before and after the change in the law). Before the changes in the law, multiple 3-year periods of employment could follow each other if there was a three-month break in-between the periods. This break has now been extended to 6 months. Together, these measures were supposed to make the difference between permanent and temporary contracts smaller and incentivize employers to hire more employees on a permanent contract.
However, at the time of writing, it is unclear whether the law has actually been effective. The number of permanent contracts in the third and fourth quarter of 2015 actually decreased compared to the number in the respective quarters in 2014 (Statistics Netherlands 2016a). In addition, there are signals that employers (especially small organizations) have become more hesitant to employ workers on a permanent contract due to the compensation at dismissal (De Koning 2016). This is mainly due to legal regulations concerning long-term illness-if employees get a long-term illness, they cannot be fired for 2 years and employers have to pay for their sick leave during this period. After these 2 years, employers can file for dismissal, but now also have to pay compensation.
Similarly, the increase in the number of self-employed persons has led to discussion and changes of laws. By some, this increase is being hailed as a sign of entrepreneurship, by others as hidden form of unemployment for those who cannot find a job (Hofs 2016;Witteman and De Haan 2016). In their newspaper article, Witteman and De Haan conclude that both are true: disproportionally many self-employed persons are either at the top or at the bottom of the income distribution. In financial and commercial services and in health care, income is the highest. In the food service industry and in the culture, sport and recreation sector income is lowest. On average, the income of self-employed persons is lower than that of salaried workers (Statistics Netherlands 2016b). There is one exception: physicians are the only group for whom the income is significantly higher as a selfemployed person than as a salaried worker.
As a large share of PhD graduates works in academia shortly after their PhD, temporary employment in academia merits special attention. As already stated in the introduction, the share of temporary employees at Dutch universities has increased over the past 15 years, the share of temporary academic employees having increased from 43 % in 1999 to 62 % in 2014 (Association of Dutch Universities 2016). Particularly within the categories of other scientific staff (a category mainly made up of postdoctoral researchers) and assistant professors (Dutch: universitair docenten), positions have increasingly become temporary. With these trends, obtaining a permanent position at a Dutch university has become more difficult over the years. Still, opportunities for a permanent position are still larger than in, for example, Germany, where researchers are appointed as research affiliates on a temporary contract for long periods of time (Kreckel et al. 2008: 352).
A large majority of recent PhDs from Dutch universities work in the Netherlands. As such, the job market that they operate in, is one of increasing flexibility. An earlier study by one of us among postdoctoral researchers in the Netherlands has shown that the temporary nature of these positions affects job satisfaction (Van der Weijden et al. 2016), and so has a study among postdocs in Germany, Austria and Great Britain (Höge et al. 2012). Still, no studies have determined the effect of temporary employment on the job satisfaction of PhDs by using a control group: PhDs with a permanent position-which is what this study sets out to do.

Job satisfaction
Job satisfaction has been defined by Locke (1969) as ''the pleasurable emotional state resulting from the appraisal of one's job as achieving or facilitating the achievement of one's job values''. Thus, job satisfaction is the result of the relation between a person's values and the extent to which the job's attributes can facilitate the achievement of these values. Many different factors can affect job satisfaction. An important one is the level of the job: a skill mismatch negatively influences job satisfaction (Allen and van der Velden 2001; Mavromaras et al. 2010). The type of employment also plays a role: in a metaanalysis Wilkin (2013) showed that non-permanent employment decreases job satisfaction. The type of non-permanent employment matters: self-employed persons are as satisfied as permanent employees, whereas agency workers and direct-hires (i.e., persons hired on a temporary contract directly by the company) are less satisfied.
Job satisfaction among (recent) PhD graduates has been assessed for several countries and regions and is generally quite high (e.g., Bender and Heywood (2006), and Moguérou (2002) for the U.S., Di Paolo (2012) for Catalonia; Kifle and Desta (2012) for Australia). Many of these studies (e.g., Bender and Heywood 2006;Di Paolo 2012;Moguérou 2002) found that PhDs working outside of academia are overall less satisfied with their job than those working in academia, although Di Paolo (2012) found that PhDs in non-academic jobs are more satisfied with pecuniary rewards. Skill matches play a large role among PhDs: a skill mismatch is associated with lower job satisfaction (Bender and Heywood 2009).
In the general labor force, multiple other factors have been shown to affect job satisfaction, and were therefore also measured in our survey (for a complete list of variables, see the methodology section). Part-time employment may have an effect, but this effect is ambiguous, with some studies finding a positive effect, some a negative one, and some none (Conway and Briner 2002). Time in job also affects job satisfaction: directly after finding a new job people are more satisfied with their job (the ''honeymoon effect''), but later they are less satisfied (the ''hangover effect'', e.g., Vroom and Deci 1971;Lawler et al. 1975;Boswell et al. 2009). Furthermore, having a mentor has been shown to contribute to job satisfaction, through an increase in self-confidence (e.g., Nick et al. 2012).
In addition, a number of personal characteristics have been found to influence job satisfaction, both in the general labor force and more specifically among academics or PhD graduates. For example, satisfaction varies by field of PhD (e.g., Moguérou 2002;Sabharwal and Corley 2009). Females tend to be more satisfied with their job than males, not because their jobs are better, but because the expectations they have of their jobs are lower (Clark 1997). However, the same paper finds that this gender difference, with women being more satisfied, disappears for the highly educated, and for persons in professional and managerial positions. Indeed, studies on the job satisfaction of PhD graduates have found female PhDs to actually be less satisfied (Bender and Heywood 2006;Moguérou 2002). Nationality also matters: US-born science and engineering faculty were found to be more satisfied with their job than foreign-born faculty (Sabharwal 2011).

Methodology Sample and survey methodology
Our survey was developed to gain more knowledge on the labor market position of recent PhD graduates from Dutch universities. Topics included job choice, perception of career prospects, use of skills developed during PhD, mentoring experiences, and the value of the PhD degree. A detailed description of the sample and survey methodology can be found in our working paper on the development of the survey questionnaire . The survey sample consisted of 2193 PhD graduates. Of these, 1023 persons obtained a PhD between April 2008 and March 2009 from Utrecht University (a large, broad research university), Delft University of Technology (engineering and technology), Wageningen University (historically focused on agriculture but now broadening its scope to life sciences and environmental research), and Erasmus University Rotterdam (focused on medicine and social sciences, especially economics, law and management). This group has been approached before in a previous survey (Sonneveld et al. 2010). Another 1170 PhDs in the sample obtained a PhD between January 2008 and May 2012 from Leiden University, which performs research in all major areas except engineering and economics. Universities in the Netherlands differ in terms of scope, but are (almost) all deemed to be of good quality and reputation, without very high or low outliers (Government of the Netherlands 2014). The universities that the respondents obtained their PhDs from are no exception.
A survey invitation was sent to the 2193 PhDs in the survey sample, as well as up to three reminders if they had yet to fill in the survey. The survey was open for 91 days. A total of 1133 respondents started the survey, a 51.7 % (partial) response rate. Of the complete sample, 43.8 % progressed to the final question (960 respondents).

Variables
The variables measured were type of employment contract, several aspects of job satisfaction, other employment characteristics (sector of employment, level of the job, part-time employment, time in job, and presence of a mentor), PhD characteristics (field of PhD, time since PhD), and personal characteristics.

Employment status
One of our main variables was employment status by type of employment contract. Workers may have a permanent job contract, a temporary contract, or be self-employed. However, temporary contracts may vary in their flexibility: workers might have the prospect of obtaining a permanent position when performing their job well, or they might not. Therefore, we made a distinction between three types of temporary contracts: permanent but in a probation period, temporary with tenure track, and temporary without the prospect of a permanence. This resulted in five employment types: permanent contract, probation period of a permanent contract, tenure track contract, temporary contract without prospect of permanence, and self-employment. Self-employed persons are those doing paid work, but who are not employed by an employer.

Job satisfaction
A total of eighteen aspects of job satisfaction were measured, regarding job content, terms of employment, and work-life balance. The questions for several variables were drawn from the Careers of Doctorate Holders Survey model questionnaire (Auriol et al. 2010).
Respondents were asked to rate the variables on a five-point Likert scale ranging from ''very satisfied'' to ''very dissatisfied''.

Other employment characteristics
In our study we distinguished three sectors of employment: academic R&D, non-academic R&D, and non-R&D. The grouping of the respondents into these categories was based on two variables: involvement in R&D and type of employer. The Organisation for Economic Co-operation and Development (OECD) distinguishes three types of R&D: basic research, applied research, and experimental development (OECD 2002). PhDs not involved in any of the three types of R&D in their main job were classified as working in non-R&D (further dubbed outside research). PhDs in academic R&D (further dubbed academia) are PhDs involved in R&D and employed at a university, university of applied sciences or college, academic hospital, or research institute. Non-academic R&D jobs (further dubbed nonacademic research) are held by PhDs involved in any type of R&D and working at another type of institution (e.g., at a private business, government institution, non-academic hospital).
Other measured job characteristics were the level of the job, full-time or part-time employment, and the time in job. We measured two aspects of job level: whether respondents had a supervisory role, and the education level normally required for their job. The four education levels were bachelor or lower, master, PhD, and professional degree (e.g., medical degree). Although some studies do not find a negative effect of overeducation on job satisfaction (e.g., García-Espejo and Ibáñez 2006), other studies do (Hersch 1991). This effect has been found to be mediated by a skill mismatch rather than an educational mismatch (Allen and van der Velden 2001; Mavromaras et al. 2010). However, as educational level is a more straightforward measure we chose this variable.
In addition, to measure experienced support in their current job, we asked the respondents whether they have a mentor. A mentor is ''a more skilled or more experienced person who serves as a role model, teaches, sponsors, encourages for the purpose of promoting the latter's professional and/or personal development'' (Anderson and Shannon 1988). As the definition of a mentor may not be self-explanatory, this definition was given to the respondents in the questionnaire.

PhD characteristics
Respondents were asked to indicate in which field they did their PhD. The fields were medical and health sciences, natural sciences (including agricultural sciences), social sciences, humanities, and engineering and technology. Fields were chosen in such a way that different disciplinary contexts could be taken into account while still allowing for sufficient power in our statistical analyses. Furthermore, we measured the number of years since PhD.

Personal characteristics
Measured personal characteristics were gender, nationality, relationship status, and having young children. All variables were measured as dummy variables: gender as male or female, nationality as having the Dutch nationality or not, relationship status as living with a partner or not, and having young children as having children below the age of six or not.

Employment status
To provide background information to the extent of temporary employment among recent PhDs, we assessed the respondents' employment status. Half of the respondents (with a job at the time of the survey) have a permanent contract (Electronic Supplementary Material Table S-1). Just over a third have a temporary contract without the prospect of obtaining permanence, seven per cent are self-employed, six per cent have a tenure track contract, and three per cent are in the probation period of a permanent contract. Types of employment contract differ by sector of work: the share of permanent contracts is highest in non-academic research, lowest in academia, and intermediate outside research. The share of PhDs on a tenure track contract is highest for academic PhDs. Finally, nineteen per cent of PhDs in non-academic research and thirteen outside research are self-employed. The share of PhDs on permanent contracts is higher for those when PhD was obtained longer ago: 40 % after 1 to 3 years and 55 % after 4 to 5 years. The difference is particularly pronounced for those in academia. 1

Job satisfaction: simple comparison of job satisfaction aspects between employment types
Now, we turn to the actual impact of temporary employment on job satisfaction. PhDs were asked to rate a total of eighteen aspects of job content, terms of employment, and work-life balance. In general, they are very satisfied with many aspects. PhDs are generally (very) satisfied with the content of their job, but less satisfied with the terms of employment and some aspects of work-life balance.
We compared different aspects of job satisfaction between the different employment statuses. The answers to the job satisfaction questions were not normally distributed over the answer categories, so we used the Mann-Whitney U test to determine whether there were statistically significant differences between the groups. We compared the satisfaction of PhDs on a permanent contract to that of PhDs with other employment statuses. This revealed that PhDs on temporary contracts are, unsurprisingly, less satisfied with job security than those on a permanent contracts, especially if they have no prospect of permanence (Fig. 1). The PhDs on a temporary contract without the prospect of permanence are also less satisfied with several other aspects, i.e., their contribution to society, salary, personal and family-related circumstances, social status, benefits, infringement of job on personal life, availability of permanent jobs within the organization, the organization's career policy and HRM, and job opportunities within the organization. The one aspect they are more satisfied with than those on a permanent contract, is the intellectual challenge of their job. PhDs on a tenure track contract and self-employed PhDs are more satisfied with this aspect as well. Furthermore, self-employed PhDs are more satisfied with their degree of independence, creativeness, level of responsibility, and social status.
1 Only for PhDs outside research the share of PhDs on temporary contracts without prospect of permanence does not go down; this is likely to be caused by the fact that many of them are residents (medical specialists in training, e.g., to train as a neurologist), which are temporary positions that can last up to 6 years for some medical specialisms.
High Educ (2017) 74:321-339 329 Job satisfaction: effect of employment status controlling for other variables Thus it appears that temporary contracts have a considerable (adverse) effect on job satisfaction, especially when it comes to terms of employment. However, it remains to be seen if this effect also exists if other factors affecting job satisfaction are taken into account.

Combination of job satisfaction variables into three scales
In the questionnaire, job satisfaction as such is not a variable: what is measured is the satisfaction with many separate aspects of the job. These have to be combined in order to Fig. 1 Job satisfaction by employment status. Depicted in the heatmap are the statistically significant differences in mean rank between different types of non-permanent employment and a permanent contract in matrix format (Mann-Whitney U test, p \ 0.05). In brown are the aspects that PhDs on a temporary contract (or being self-employed) are less satisfied with than those on a permanent contract; in blue the ones that they are more satisfied with. The brighter the color, the larger the difference. Heatmap generated using the R package gplots. (Color figure online) obtain a job satisfaction variable. We did not combine all aspects into a single variable, but instead defined three job satisfaction scales: job content, terms of employment, and worklife balance based on exploratory factor analysis using principal component extraction and promax rotation (Table S-2). After factor analysis, the reliability of the three scales was determined. For the scale of satisfaction with work-life balance, the Cronbach's a score was lower than 0.7. Therefore, two variables, satisfaction with travelling distance and with personal circumstances, were excluded. After removal of these items the Cronbach's a scores were at least 0.77 for all three scales. For the satisfaction with work-life balance scale the average score on the two items was computed. For the scales on satisfaction with job content and with terms of employment, the average score was computed if four or more items out of the seven scale items were answered.

Satisfaction with job content
We ran a linear regression of job satisfaction on both employment status and other characteristics. These characteristics were other employment, PhD and personal characteristics. Table 1 shows the results of the regression of the three job satisfaction scales on employment status and the other characteristics. In our analyses, we tested for interaction between gender and having children, but no interaction was found and thus not included in the model. Self-employment increases the satisfaction with job content, whereas temporary contracts without prospect of permanence decrease it. Thus, employment status influences satisfaction with job content. Like Wilkin (2013), we show that the type of ''non-permanence'' matters, with self-employment not decreasing satisfaction with job content (rather increasing it), whereas temporary contracts without prospect of permanence do decrease it (albeit to a small extent). Thus, our results indicate that for PhDs, self-employment is an attractive option, as it gives them more satisfaction with degree of independence, level of responsibility, intellectual challenge, creativeness and social status (see Fig. 1). Self-employed PhDs appear to be part of the group of self-employed persons in the Netherlands who mainly reap the benefits of self-employment, instead of the group who is self-employed because they cannot find employment at an employer (Witteman and De Haan 2016). From these results, a policy implication could be that PhDs should be encouraged to set up their own businesses. Self-employed PhDs do, however, differ from other PhDs in one aspect: age. At the year of PhD, they were on average 41 years old, whereas those now employed on a permanent contract were on average 35 years, and those on temporary contracts between 31 and 32. Therefore, it may be their work experience that makes selfemployed successful and thereby satisfied with their jobs, rather than (just) the fact they are self-employed.
The level of the job matters, too: having a supervisory role has a positive effect on job satisfaction, whereas having a job below PhD level has a negative influence. This negative effect of working below PhD level on the satisfaction with job content is in accordance with Bender and Heywood's study (2009), which found that skill mismatches are associated with lower job satisfaction among U. S. PhD graduates. The mismatch between educational attainment of PhDs and job level is not a marginal phenomenon, as more than twenty per cent of PhDs indicate they have a job at master's level, and another two per cent a job at bachelor level or lower. These shares are higher for PhDs outside academia than in academia ( Table 2).
The finding that skill mismatches are a strong negative influencer of satisfaction and that they are more prevalent outside academia has an important implication. Previous Table 1 Effects of employment, PhD and personal characteristics on three scales of job satisfaction ( studies have found that PhDs working outside academia are less satisfied with their job than those working in academia (e.g., Bender and Heywood 2006;Moguérou 2002). However, we do not find such an effect of employment sector when type of employment and required educational level are controlled for. This is a consequence of the relation between sector of employment and required educational level. As such, it is the job's required educational level that affects satisfaction with job content, rather than sector of employment itself.
Our results indicate that outside academia, PhDs have more trouble finding jobs that are intellectually challenging and that offer autonomy, values they find very important in their job choice (e.g., Roach and Sauermann 2010;Bloch et al. 2015;Waaijer 2016). The current study shows that not only are jobs outside academia less attractive to PhDs due to the relative lack of these job qualities, they also decrease job satisfaction.

Satisfaction with terms of employment
A temporary contract (both tenure track and without the prospect of permanence) negatively influences satisfaction with terms of employment. A supervisory role increases satisfaction, as does having a mentor in the current job, and working outside academia. The latter mirrors Di Paolo's finding (2012) that PhDs outside academia are more satisfied with their pecuniary rewards. A job at bachelor level or lower in turn negatively influences satisfaction. Also for terms of employment a longer time in job decreases satisfaction: the hangover effect (Vroom and Deci 1971;Lawler et al. 1975;Boswell et al. 2009).

Satisfaction with work-life balance
Having a tenure track contract negatively influences job satisfaction with work-life balance, as does having a humanities PhD, and having a job at professional degree level. The negative effect of having a tenure track contract is likely to be a result of the pressure to succeed when having such a contract. A likely explanation for those with a job at professional degree level having lower job satisfaction is that many of these PhDs are medical doctors, whose jobs are highly demanding and among whom stress and burn-out are relatively prevalent (Prins et al. 2010;Visser et al. 2003). In addition, female PhDs are less satisfied. This is a common finding in other studies on female and male academics (e.g., de Lourdes Machado-Taylor et al. 2014). Finally, the longer a PhD has had a job, the less satisfied they are.

An extra variable: part-time employment
An important employment characteristic that could have influenced job satisfaction was whether a respondent had a full-time or part-time job contract (Conway and Briner 2002). This question was only put to employees and not to self-employed respondents, for whom the distinction between part-time and full-time is problematic. Thus, we performed this linear regression without self-employed PhDs (Table S-3). The results show that most effects remain statistically significant. Most importantly, the negative effects of the different types of temporary contracts on job satisfaction, particularly with terms of employment, but also with job content and work-life balance are also apparent in the second model. Part-time employment itself negatively influences satisfaction with terms of employment.
Overall effect of temporary employment on job satisfaction We now make a complete assessment of the effect of temporary employment on job satisfaction. The largest effect is on satisfaction with terms of employment: in a simple comparison, the job satisfaction of PhDs on temporary contracts is lower than that of their peers on permanent contracts, unsurprisingly especially regarding job security. In this simple comparison, PhDs on temporary contracts are actually more satisfied with one of the aspects of job content, namely the intellectual challenge in the job. The lower satisfaction of PhDs with terms of employment in the simple analysis when employed on a temporary contract, is counteracted by a slightly higher satisfaction with the intellectual challenge in the job. However, we also found that when other factors, such as the sector of employment and level of the job are controlled for, there is no positive effect of temporary contracts on satisfaction with job content. Instead, temporary contracts (without prospect of permanence) turn out to be a slight negative influencer of satisfaction with job content. This is due to the role that sector of employment and required education level of the job play. Many recent PhDs on a temporary contract work in academia, where they have a higher chance to work on their level of educational attainment than their peers outside academia. When the level of the job is controlled for, the ''positive'' influence of temporary employment found in a simple comparison disappears.

Effect of employment status on personal life
The respondents were also asked what effects their type of employment contract had on their personal lives. Items were the ability to obtain a mortgage, the stability of their family lives, and the possibility to start a family. PhDs on a permanent contract were asked to which extent their contract had positively influenced these items and PhDs on a temporary contract to which extent it had negatively influenced them. The type of contract has the largest effect on the ability to obtain a mortgage. Four in ten PhDs on a temporary contract say their contract type has ''much'' or ''very much'' negatively influenced this ability. For the ones on a permanent contract this share is even higher: seven in ten say their permanent contract has positively influenced the ability ''much'' or ''very much''. With respect to the stability of family life and the possibility to start a family the effects are smaller, but still considerable: roughly a third of PhDs on a temporary contract say this contract ''much'' or ''very much'' negatively influenced their families. Men and women do not differ in a statistically significant way. As PhDs in academia are more prone to have a temporary contract, the effects of temporary contracts on personal lives are particularly pronounced in academia.

Conclusions and policy implications
According to dual labor market theory, temporary employment negatively affects the job satisfaction and well-being of workers, and disparities between workers on temporary contracts and those on permanent contracts tend to persist. However, it is also hypothesized that the highly educated may be exempt from this negative effect, and may use temporary jobs as a stepping stone to permanent employment. Our analysis shows that for PhD graduates, temporary jobs are not ''bad'' jobs in the true sense of the word: if anything, PhDs on a temporary contract are more satisfied with job content. But, when we control for sector and job level, we find a negative influence of temporary employment on satisfaction with both job content (small effect) and terms of employment (larger effect). This shows that a negative effect of temporary employment also exists for (recent) PhD graduates, the highest educated persons in the labor force. Our findings are in line with Bertrand-Cloodt et al. (2012) and Van der Meer and Wielers (2014), who found that the highly educated (those with a university degree) are not exempt from the negative effects of temporary employment. We expect this is because temporary employment can lead to insecurity about career prospects, which in turn affects job satisfaction, as also found by Van der Weijden et al. (2016) among postdoctoral researchers (by definition employed on a temporary contract). As such, on the whole the PhDs studied here do not appear to experience a balanced psychological contract as found by Lam and de Campos (2015). However, further qualitative research would be needed to study which psychological contract PhDs experience with their employers, whether subgroups can be discerned, and whether the effects of temporary employment differ by psychological contract. Finally, we find a negative effect of temporary employment on the personal lives' of recent PhD graduates.
In conclusion, temporary employment negatively influences the job satisfaction of recent PhD graduates. Temporary contracts are much more prevalent in academia than outside it, making this effect especially important for the human resource management at universities and other academic institutions. Our results strongly suggest that whereas universities offer jobs that satisfy PhDs intellectually, they could much improve their relative attractiveness on the labor market by increasing the share of permanent contracts and contracts with the prospect of permanence to levels comparable to those in other sectors. Furthermore, since we found that almost a quarter of PhDs indicate they work below PhD level, we may conclude that there is a mismatch between the number of PhD conferrals and the demand for PhD graduates outside academia, where PhDs are overqualified for the labor market. This mismatch may well be exacerbated by the current growth of the number of PhDs (Association of Dutch Universities 2016).
However, the mismatch may also lie in the types of skills obtained during a PhD trajectory in the Netherlands, and actually concern an underqualification. To check this, the match between acquired and required skills for various job types has to be studied. Actually, in our survey, we also collected information on the extent to which PhDs developed certain skills during their PhD and to which extent they need them in their current job. Preliminary data (to be reported elsewhere) show that research skills are overdeveloped by PhDs outside academia, but personal effectiveness, management and communication skills severely underdeveloped. This means that not only are PhDs working at bachelor or master level overqualified (looking purely at their degree), they are also underqualified, as they did not develop the skills needed for their current job in their doctoral training. This, too, could have a negative effect on job satisfaction. Thus a major policy implication is that Dutch universities should broaden their doctoral training to not only include the development of research skills, but also skills in other areas.