The impact of factors on information sharing: An application of meta-analysis

Background Information sharing plays a key role in supply chain performance. According to previous individual studies, technology, trust, commitment, and uncertainty are four potential factors affecting information sharing. However, most studies focus on testing a positive relationship between each factor and information sharing. Therefore, it is necessary to evaluate the effect of each factor on information sharing. Objective To determine the accurate effect of factors on sharing information and propose key factors to support decision-makers in improving their information sharing. Data Correlation coefficients between factors are collected from 41 individual studies with a total of 8,983 samples on Google Scholar Methods Using the rank correlation test and Egger’s regression test to test publication bias. The meta-analysis method is used to perform analysis models, including fixed-effect, random-effect, and Hunter and Schmidt methods Results Commitment plays the most important role in information sharing when compared to technology, trust, and uncertainty. Commitment accounts for 19% in the Hunter and Schmidt method and 22% in both fixed-effect and random-effect models. In addition, the result indicates that there are around 50% of other factors that affect the efficiency of sharing information besides four factors in our studies. Conclusion Technology, trust, and commitment significantly affect information sharing, of which the impact of commitment on information sharing is strongest and should be a priority in improving the effectiveness of information sharing. Our study contributes two findings to literature in the field of supply chain information sharing: 1) certain confirming the important role of commitment on sharing information, and 2) the necessity of considering other factors besides these four elements.


Introduction
"Information sharing (IS)" refers to the activity of exchanging good-quality information or knowledge among partners who work collaboratively as a single entity in the supply chain [1]. Thus, the term "information sharing" may be known as "knowledge sharing" or "information integration" [2]. Information sharing seems to be the heart of connection in the supply chain [3]. It brings many benefits to each supply chain member in particular and the whole supply chain in general [4]. Lotfi et al. [5] point out that information sharing reduces supply chain vulnerability. According to Gavirneni et al. [6] supplier's costs dropped 1-35% by sharing inventory information. Lee and Whang [7] and Lee et al. [8] demonstrate that exchanging information among supply chain members may decrease both inventory and associated costs significantly. Besides, the effect of uncertainty in the supply chain reduces significantly due to sharing information among partners [9]. Uncertainty is a consequence of lacking information, which creates the bullwhip effect in the supply chain. The information flows, exchanged among supply chain members, strongly limit the negative impact of the bullwhip effect [10]. Furthermore, information sharing also helps to improve resource utilization [11], the efficiency of products and services [12], and the quick response under the change of market [13], as well as increasing social relationships [7].
Technology, trust, commitment, and uncertainty are four potential factors that are indicated their importance with information sharing by many previous individual studies. Khurana et al. [14] demonstrate that technology or technological capacity is a key barrier to information sharing. Omar et al. [15] confirm the positive impact of technology on information sharing. Technological linkages are particularly critical to transfer information flows among supply chain members effectively [16], and a poor technology significantly affects the information transmission process even interrupts the movement of information among stakeholders in the supply chain [17]. However, the support of technology may be ineffective without each firm's willingness to share information [18]. The willingness of sharing information is defined as an openness attitude of individuals to exchange the necessary information to supply chain partners honestly, enthusiastically, and reliably [19]. Zaheer and Trkman [20] and Wu et al. [21] indicate that trust and commitment are two main factors in the willingness to share information. Trust is defined as a term of the perceived reliability and honesty among stakeholders [22,23]. Commitment is described as a promise or agreement which is towards a long-term and enduring relationship [24]. Finally, Şahin and Topal [25] indicate that information sharing is affected by uncertainty. Uncertainty is described as competition uncertainty, the change of technology, demand fluctuations, and the uncertainty of suppliers and customers [26]. However, almost all previous studies only consider the relationship of one factor or two factors on information sharing (Table 1). For example, Li et al. [27] only consider the relationship between trust and information sharing. Technology and uncertainty are introduced by Sundram et al. [28]. Wong et al. [29] indicate that technology has a positive relationship with information sharing. Besides, almost all previous studies determine the positive influence or relationship between factors and information sharing. They mainly use primary analysis to find the answer to their research questions. Therefore, it is necessary to evaluate the influence of all four factors on information sharing, compare and determine which factors have the strongest influence on information sharing.
In this study, all four elements: trust, technology, commitment, and uncertainty are considered. The aim of this study is to determine the accurate influence of factors on information sharing. From that, keys factors are proposed to support decision-makers in improving their information sharing. The method of meta-analysis is used in this study. The term "meta-analysis" is as known as a quantitative research approach to summarize, analyze, and compare results from the empirical literature. Unlike primary analysis and secondary analysis, metaanalysis statistically analyzes the results of multiple studies instead of one study. Hence, its results are inferences drawn from a sample of studies. In addition, its results are the form of effect sizes. These effect sizes are usually calculated from data published in papers, which means that the raw data is non-obligatory. Correlation coefficients are used to compute the effect sizes in our study. Correlation coefficients are collected from 41 relevant individual studies obtaining a total of 8,983 samples. Our results show that commitment plays a key role in sharing information when compared with trust, technology, and uncertainty. This conclusion is our contribution to the literature on the supply chain field. In addition, our study also emphasizes that there are many other factors influencing information sharing that should be considered.

Definition
Technology. Technology or information technology refers to the activities of storing, retrieving, transmitting, and manipulating data or information in computers. Information technology plays a key role in supply chain management in general and in sharing information in particular [15]. The roles of information technology are introduced by numerous previous studies. Rajaguru and Matanda [39] identify that the role of information technology is as an inter-organizational information system. They link individual information technologies to

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The impact of factors on information sharing transfer information between supply chain members effectively. Similarly, Ye and Wang [37] introduce the term information technology alignment to describe the connectivity and compatibility of the information technology infrastructure in the supply chain. Term of IT infrastructure presents a physical connection to support information exchange among partners [20]. Finally, IT enablers are relevant technologies and/or equipment to increase the transmission speed, accuracy, and security during the whole process of sharing information in the supply chain [40]. Thus, IT conceptualization mainly focuses on information connections and technological supports in sharing information [34].
Trust. Trust is defined as a term of the perceived reliability and honesty among stakeholders [41][42][43]. Trust is also known as a reliable expectation that an organization brings to its partners to fulfill obligations based on their cooperation [44,45]. Trust is bidirectional in ensuring integrity among supply chain members [46]. For instance, customers trust suppliers to deliver their products on time and providing an agreed price. Equally, suppliers believe that their customers complete payments in line with agreed terms.
Commitment. "Commitment is defined as the desire on the part of each party to a business relationship to maintain and strengthen that relationship" [44]. A business relationship is described as a connection between entities engaged in commercial activities. That consists of the relationships between different relevant individuals in any business network [47]. Allen and Meyer [48] indicate that commitment obtains the aspects of affection and continuation. This means that each member in a committed relationship is willing to lose short-term benefits to maintain a long-term relationship [49]. Similarly, in the supply chain, the term of commitment is known as a promise or agreement formed a long-term and active relationship between supply chain members during the process of working together [24]. Supply chain members are willing to contribute some business benefits to a sustainable relationship [50,51].
Uncertainty. Uncertainty is defined as "the difficulty firms have in predicting the future"

Hypothesis development
In our study, the most common areas derive from selected publications. They are the relationships between technology and information sharing, trust and information sharing, commitment and information sharing, and uncertainty and information sharing. Based on hypotheses from relevant studies reviewed and examined in the meta-analysis, our hypotheses are formed.
Hypothesis 1: The more trust, the more effective information sharing is Panahifar et al.
[58] emphasize the important role of trust in sharing information. Information exchange becomes more free and reliable when individuals have a high trust relationship. This statement is similar to the conclusion found by Cai et al.
[33] that confirm the positive influence of trust on sharing information between Chinese firms and their suppliers. Similarly, Khan et al. [59] indicate that trust and information sharing have a positive relationship when they research the sustainability of service supply chain management. In addition, trust significantly affects the extent of information sharing [60]. Open and honest information sharing will improve information asymmetry among partners and enhance long-term cooperation [61].
Hypothesis 2: Information technology has a positive influence on information sharing In information sharing, technology plays a key role in empowering companies to access or exchange information [15]. Besides, it seems to be a bridge to connect individual information technologies to form an information network [39]. This leads to the efficiency of communication between firms by receiving high-quality information and the rapid time of exchange [62]. Thus, the relationship between technology and information becomes more closely. Somjai and Jermsittiparsert [36] indicate that the ability of technology directly affects information sharing.  [66]. Similarly, Li and Lin [40] form the hypothesis that when the level of uncertainty is higher, information sharing tends to increase sharply. Based on the results of an investigation, Jia et al. [67] indicate that the uncertainty drives the strong development of sharing information between supply chain members.

Publication selection strategy and publication bias tests
A systematic literature review of studies about information sharing in the supply chain is performed. Search terms related to information sharing or information exchange are used to find publications from 2010 to March 2021 on Google Scholar. They include the terms "information sharing" and "supply chain", "exchanging information" and "supply chain", "factors" and "information sharing" and "supply chain", "factors" and "information exchange" and "supply chain", "potential factors" and "information sharing" and "supply chain", or "common factors" and "information sharing" and "supply chain". Selected publications based on different criteria in each step. First of all, after reviewing the title and keywords in the article, duplicate articles and omitted search terms about information sharing or supply chain will be removed. Second, the full abstract of articles is considered carefully. A suitable abstract consists of 1) relating to sharing information in the supply chain field and 2) providing completely the objective, methodology, and conclusion. Third, all sections of the paper are fully reviewed to select the articles entirely in English and consider the relationship between factors and information sharing. Finally, suitable articles for this study are selected. This selection depends on criteria, including 1) belonging to the area of information sharing in the supply chain, 2) introducing factors affecting information sharing, and 3) containing correlation coefficient and sample size.
To test publication bias, the funnel plot, the rank correlation test, and Egger's regression test are proposed [68]. "Funnel plots are simple scatterplots of the treatment effects estimated from individual studies against a measure of study size [69]". The rank correlation test and Egger's regression test are used to evaluate the relationship between effect estimates and sampling variances. In both the rank correlation test and Egger's regression test, if the p-value is less than 0.05, the funnel plot is asymmetric. Unlike the rank correlation test, Egger's regression test is a good candidate for smaller meta-analyses (less than 25 studies) [70,71]. In this study, therefore, Egger's regression test is selected to test publication bias, and this process is performed by Rstudio-Rx64 4.3.0 In this study, initially searching for relevant publications is mainly conducted by one author (Chau Thi Diem Le). Then, all candidate articles are read, checked their suitability with stated criteria, and selected suitable articles for analyzing models in this study by three authors (Chau Thi Diem Le, Miklós Pakurár, and Judit Oláh). In some cases, if there are any disagreements, they will be solved by discussing with the fourth investigator (István András Kun).

Data selection
Based on meta-analysis methods [72][73][74][75] [100], these number of observations are enough ability to provide reliable results in our study. Our data are shown in Table 2

Meta-analysis
Meta-analysis refers to a quantitative research method to synthesize and compare results of the empirical literature [101]. Especially, "meta-analysis is a statistical tool for estimating the mean and variance of underlying population effects from a collection of empirical studies addressing ostensibly the same research question" [100]. Unlike primary and secondary analysis, metaanalysis has some highlight differences in data and conclusions. In a meta-analysis, the statistical results from multiple studies of an event are summarized, analyzed, and compared quantitatively. Hence, its conclusions are inferences drawn from a sample of studies [102]. In addition, the data in meta-analysis is collected completely from the statistical results of multiple studies. Thus, the original data is non-obligatory in meta-analysis while it is the most important element in the primary and secondary analysis [103].
Field and Gillett [100] propose six steps to perform a meta-analysis, as follows: 1) Searching for publications, 2) Evaluating the suitability of publications by the criteria of the study, 3) Computation of effect size, 4) Implementing basic meta-analysis, 5) Performing in-depth analysis, and 6) Reporting results. According to Glass [102], two methods are popular in metaanalysis: 1) "fixed-effect model" and "random-effect model" are developed by Hedges and colleagues [72][73][74], and 2) "Hunter and Schmidt method" [75].
Field [104] indicates that the transformation or no transformation of correlation coefficient and the weights of study create the difference between methods. In the "Hunter and Schmidt method", Hunter and Schmidt [75] propose some equations to calculate the mean effect size,

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The impact of factors on information sharing the squared standard deviation of weighted sample, interval estimation, and the homogeneity of effect size. This is described clearly by equations, as follows: • The mean effect size: Whereas k is the number of studies, n i is the total of sample of study i, r i is the correlation coefficient between two variables of study i • The squared standard deviation of weighted sample: Whereas k is the number of studies, n i is the total of sample of study i, r i is the correlation coefficient between two variables of study i, � r is the mean effect size • Interval estimation: Whereas � r is the mean effect size; s 2 • The homogeneity of effect size: Hedges and colleagues, equations are formed to calculate Fisher's z values, the transformed effect size, variance, and the homogeneity of effect sizes in their methods. Eqs (6)-(12) are used for the fixed-effect model, and Eqs (13)- (16) are to calculate the values in the randomeffect model. Fixed-effect model: • Fisher's z values: Whereas r i is the correlation coefficient between two variables of study i • The transformed effect size: Whereas w i is the weight of study i; • Sampling variance of the average effect size: • The variance at Fisher's z value: • The standard error: SEð � z r Þ ¼ ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi • Chi-square statistics: Random-effect model: In two methods proposed by Hunter and Schmidt and Hedges and colleagues, the calculation of effect size is required. The effect size is the currency in a meta-analysis, which also reflects the large size of the relationship strength between the two variables in a population. The measure of effect sizes may be based on mean, risk ratio, odds ratios, risk difference, and correlation [68,75,100]. In our study, the application of three models of Hunter and Schmidt and Hedges and colleagues is performed. The effect sizes represent the relationship between information sharing and each factor. The correlation coefficient is used as a measure between these relationships. Eq (1) is used to compute effect size in Hunter and Schmidt method. Similarly, effect sizes are also calculated by Eqs (6) and (13) in the method of Hedges and colleagues. In particular, the correlation coefficient is often transformed to Fisher's Z r to perform analysis and comparison in meta-analysis [68]. The reason for the transformation process is that the sampling distribution r is skewed around a given population ρ. By contrast, the sample of Z r is symmetrical around a population Z r . The symmetry of the sample of Z r need to perform the comparison and combination of effect size across studies [74]. Other equations are additional equations supporting the further coding process.
In this study, the overall process is also followed by six steps of Field and Gillett [100]. Firstly, keywords are used to find publications. Then, the criteria of study are formed to select suitable publications. The formulation of criteria is based on our objective evaluation. Next, the correlation coefficient and the population correlation coefficient are used to calculate effect size and other values in models [75,100]. Fifthly, the goodness of study is measured to determine the reliability of the meta-analysis [75,105,106]. According to Rosenthal [107], this measure is performed by Eq (17) determining the fail-safe number. "The fail-safe number represents the number of studies required to refute significant meta-analytic means [108]". If the number of studies is larger than the value of fail-safe N when multiplied by five and added by ten, the number of studies is reliable [100,106]. Finally, our results are summarized and written as a complete report.
• The fail-safe number:

Study selection
By the initial search, there are 750 identifiers of related publications. Subsequently, 310 studies are excluded for duplication and lack of relevance. Then, 173 articles are not included because they do not meet one of all of the abstract's requirements. After reviewing full articles, 107 relevant publications are selected. These studies mainly focus on the relationship between factors and information sharing in the supply chain. Finally, 47 articles are used to analyze relevant models in this study because they contain both the necessary information and required data. Following PRISMA 2020 flow diagram [109], the results of publication selection are described in Fig 1. Based on Egger's regression test, the results of the publication bias test are shown in Table 3. These results are performed by Rstudio software-Rx64 4.0.3. Table 3 shows that p

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The impact of factors on information sharing values of the four factors range from 0.14 to 0.99 and they are greater than 0.05. Therefore, it is undoubted that there is no publication bias.

The results of analysis models
Using correlation coefficient. Table 4 shows the results of the correlation coefficient between factors and information sharing in three models. In particular, Eq (1) is used to find the correlation coefficient in Hunter & Schmidt column. For the fixed-and random-effect models, correlation coefficients are calculated by Eq (6). According to Cohen [110], the range of correlation between factors and information sharing is distributed at small, medium, and large levels. Particularly, commitment has the largest effect on information sharing while the relationship between uncertainty and information sharing is lowest in all three models. Meanwhile, the relationship between technology and information sharing and the correlation between trust and information sharing obtain both moderate and high effects.
On the other hand, the difference between the largest and narrowest values of correlation coefficient in Hunter & Schmidt, fixed-effect model, and random-effect model is 0.3, 0.4, and 0.3, respectively. This means that there exist other factors besides those considered influencing information sharing. The impact of our factors on the variance of information sharing is higher than the effect of other elements in all three models (72% in the Hunter & Schmidt model, 79% in the fixed-effect model, and 86% in the random-effect model). In which, the degree of commitment influence on information sharing variance is the highest (26% in Hunter & Schmidt model, 29% in fixed-effect model, and 31% in random-effect model). The second and third major influence is trust and technology, respectively. In contrast, the lowest impact on information sharing variance is uncertainty (3% in Hunter & Schmidt model, 4% in the fixed-effect model, and 6% in the random-effect model).
The largest effect of information sharing is commitment. The fact remains that commitment is an important key to maintain and develop trust in a relationship [111]. Having a good or sustainable relationship makes individuals more willing to communicate more informally with their partners [112]. They can easily exchange more accurate and important information. This increases the efficiency of information exchange [113]. Next, trust has the second-largest correlation to information sharing. The role of trust is similar to the commitment which creates sustainable relationships. However, trust is difficult to measure because its origin is the behavior of each individual [41] while commitment may be measured thanks to agreements. This may lead to the lower effect of trust on information sharing when compared with commitment [24]. Thirdly, the effect of technology and trust on information sharing is approximate. The reason for this may be that technology can be seen as supporting equipment or bridge the activities of individuals in the supply chain [114]. Therefore, in information sharing, technology only plays a role as a person who transmits information quickly and accurately [39]. Finally, the impact of uncertainty on information sharing is the lowest. According to Fynes et al. [115] and Li et al. [116], good coordination or a close relationship is the main

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The impact of factors on information sharing cause to reduce the effect of uncertainties on information sharing [117]. Individuals who own close relationships or have strong coordination with others may be received special information that outsiders cannot access [115,116]. Calculating confidence intervals is performed to analyze the difference among correlations [105]. Eq (3) is used to find the confidence interval in Hunter & Schmidt. In the fixed-and random-effect model, the calculation of confidence interval is similar. Firstly, the values of � z r and SEð � z r Þ are used to determine the confidence interval of Fisher's z values (z r i ). Then, Eq (6) is reversed to transform the value of z r i to correlation. Results of the confidence interval are shown in Table 5. Table 5 presents that the largest confidence intervals are in Hunter & Schmidt model while confidence intervals in fixed-effect are the lowest. Confidence interval width describes a great variety of articles. Under Hunter & Schmidt model, the larger the confidence interval width proves that more studies are included. However, the situation is reserved under the randomeffect model.
In Table 5, due to the largest confidence intervals, the difference among correlations is analyzed based on the results in Hunter & Schmidt model. In this model, factors of uncertainty have a negative value. This means that uncertainty has no effect on information sharing. The confidence interval width of uncertainty is widest while the confidence interval magnitude of trust is narrowest. These orders are changing under the random-effect model. The results of the confidence interval are suitable with the above correlation coefficient results.
According to Borenstein et al. [118] and Walker et al. [119], on the other hand, the confidence interval under the random-effect model is larger than that under the fixed-effect model because of the heterogeneity of studies. Thus, the homogeneity test is performed in our study. "It is common to use a test for homogeneity to determine if the results of the several experiments are sufficiently similar to warrant their combination into an overall result [120]". Eqs 5 and 12 are used in Hunter & Schmidt and the models of Hedges and colleagues, respectively. Our results are shown in Table 6.

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The impact of factors on information sharing Some limits are calculated to find the homogeneity. Based on the Chi-Square probabilities table, limits are as follows: 22.362 for the technology, 26.296 for the trust, 21.026 for the commitment, and 15.507 for the uncertainty. As a result, the hypothesis of homogeneity cannot be rejected in the random-effect model while heterogeneity occurs in both Hunter & Schmidt and the fixed-effect model. Hence, there may be the appearance of an effect in Hunter & Schmidt and the fixed-effect model unavoidably. In addition, this test result is consistent with the results of the above confidence intervals-high heterogeneity, wider confidence interval.
Finally, the calculation of the fail-safe number is performed to determine the reliability of the number of articles using Eq 17. The fail-safe numbers of factors are presented as follows: 1) technology: 2797 (264 required), 2) trust: 4028 (402 required), 3) commitment: 2481 (314 required), and 4) uncertainty: 2037 (19 required). Therefore, finding too many articles is unnecessary in research. However, in the case of more studies being added, the relationship between the factors will be shown more clearly [121].
Using partial correlation coefficient. The relationship between each factor and information sharing is further clarified thanks to the calculation of the partial correlation coefficient. Partial correlation coefficient represents a relationship between independent variable-X and the dependent variable-Y when eliminating the influence of control variable-Z [75]. The partial correlation coefficient is considered a correlation coefficient when used. Thus, the calculation of the partial correlation coefficient and the correlation coefficient is similar to each other (Eq 1). Table 7 shows the results of the partial correlation coefficient in three models. Factors have a weak and moderate partial correlation to information sharing [110]. The weakest effect on information sharing is uncertainty. By contrast, the effect of technology, trust, and commitment on information sharing is stronger in all three models. In particular, the strongest correlation is determined by the relationship between commitment and information sharing. Here, trust is the second-largest impact on information sharing. The relationship between technology and information sharing is weakest when compared to other factors in the moderate group.
On the other hand, 0.3 is the difference between the largest and smallest partial correlation coefficient in all three models. This statement leads to the presence of other factors affecting information sharing. To evaluate the effect of both factors considered and other factors on information sharing, R-squared is measured. Our factors' influence on information sharing variance accounts for 49%, 52%, and 53% in Hunter & Schmidt, fixed-effect model, and random-effect model, respectively. Particularly, the commitment influence on information sharing variance is the highest (19% in the Hunter & Schmidt model, 22% in the fixed-effect model, and 22% in the random-effect model). In contrast, the percentage of uncertainty only accounts for 2% in both Hunter & Schmidt and the fixed-effect model and 3% in the randomeffect model. The orders of the impact of trust and technology are unchanged-second and third position, respectively. As a result, the attendance of other factors contributes 51%, 48%,

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and 47% to information sharing variance in Hunter & Schmidt, fixed-effect model, and random-effect model, respectively. These results are shown in Fig 2. The positive effect of commitment on information sharing is explained similarly as above. The magnitude of the direct effect of trust describes its importance in the field of information sharing. This conclusion is true because trust brings more efficiency than technology in sharing information.
Based on the confidence interval, the range of most likely values in the population correlation is shown. Besides the calculation of confidence interval shows how real the result is. The results of the confidence interval are shown in Table 8. Table 8 shows that the largest confidence intervals are found by Hunter & Schmidt model while the fixed-effect model provides the smallest confidence intervals. The analysis is focused

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The impact of factors on information sharing on the value of the Hunter & Schmidt model because of its high confidence intervals. Besides, there is the appearance of negative value in the relationship between uncertainty and information sharing. This may lead to the direct negative impact of them on sharing information. The diversity of studies is reflected by the magnitude of the confidence interval. Hence, the test of homogeneity is necessary to measure whether the number of studies involved is homogeneous. Table 9 shows the results of the homogeneity test in three models.
Some of the values of limitation are found to decide the homogeneity, including 15.507 for technology, 19.657 for trust, 16.919 for commitment, and 12.592 for uncertainty. As a result, it is undoubted that there may be the appearance of heterogeneity in both Hunter & Schmidt and the fixed-effect model. In contrast, the rejection of homogeneity is not possible in the random-effect model. These results seem to be suitable with the results of the confidence interval test.
In order to find the reliable numbers of articles, finally, the calculation of the fail-safe number is performed. The results show that our observations are enough reliability to implement the analysis of three models and draw conclusions. The fail-safe numbers of factors are as follows: 1) technology: 1452 (65 required), 2) trust: 2903 (183 required), 3) commitment: 1884 (164 required), and 4) uncertainty: 1639 (4 required). Thus, searching for many publications is non-obligate in research. However, if the publications are further added, the relationship between the elements will be shown more clearly.
In summary, some critical findings are determined in our study, which may be useful for managers to improve the efficiency of sharing information. Firstly, commitment, trust, and technology are three critical elements that should be invested by managers to increase the success of sharing information. Especially, managers should prioritize the establishment of commitment over trust and technology because of the significant effect of commitment on information sharing. In the fact, commitment is a fundamental foundation to build trust between individuals. Simultaneously, commitment is the main cause to create long-term and sustainable cooperation. Another finding is that the efficiency of sharing information is influenced by around 50% of other factors besides four factors in our studies. Thus, managers or researchers may extent the further research scope to improve better information sharing.

Discussion
Our study introduces one of the key problems in the field of information sharing in the supply chain. Our problem focuses on accurately determining the effect of factors on information sharing using meta-analysis. The factors selected are those considered by many previous individual studies to examine the positive relationship between factors and information sharing. They are technology, trust, commitment, and uncertainty. There are four hypotheses formed in our study, including 1) the greater the trust, the more effective the sharing of information, 2) information technology greatly promotes the success of sharing information, 3) there is a positive relationship between commitment and information sharing, and 4) the higher the degree of uncertainty, the stronger the level of information sharing. The characteristics of this study create a gap between our study and previous studies. Our study simultaneously considers all four factors while previous studies only examined one, two, or three factors. In addition, this study accurately determines the influence of each factor on information sharing instead of just testing their positive effect or relationship on information sharing. This means that the effect of each element is evaluated, and the most important factor is proposed in our study. Besides, our conclusions are drawn from a sample of studies due to applying the meta-analysis.
Our results show that three factors: technology, trust, and commitment affect information sharing significantly while the effect of uncertainty on information sharing is extremely weak. In the case of commitment, a strong effect of commitment on information sharing is found. The widest confidence interval is determined by the Hunter-Schmidt model. This is well worth further exploration. High heterogeneity in both Hunter-Schmidt and fixed-effect models associates with this finding. After filtering out other effects, commitment moderately affects information sharing.
For trust and technology, their impact on information sharing is moderate. The analytical findings are moderate, of which, the influence of trust on information sharing is higher than the correlation of technology. The largest confidence interval of each factor is also found in the Hunter-Schmidt model. Negative values and zero do not appear in the confidence interval. Their data is highly heterogeneous which is shown in all models except the random-effects model. Similarly, the findings of using the partial correlation coefficient also confirm a moderate direct effect of both trust and technology on information sharing. However, the confidence interval and variance when using the partial correlation coefficient are relatively small, especially for technology. This means that there are other variables that affect the correlation coefficient in the articles.
Uncertainty has a weak relationship with information sharing. Its confidence interval contains a negative value. Therefore, doubt should be raised when discussing the influence of uncertainty on information sharing. The variability of data is described by its confidence interval and heterogeneity in the Hunter-Schmidt and fixed-effect model. Uncertainty also has a weak direct effect on information sharing when using the partial correlation coefficient.
All the hypotheses have been confirmed. This study encourages managers or decision-makers to focus on improving and enhancing their business's commitment, trust, and technology with supply chain partners. This may support individuals and their stakeholders to increase the effectiveness of information sharing, reduce risk and uncertainty, and achieve a successful supply chain performance [24,39,114,117]. In some cases, managers or decision-makers are forced to improve one of three factors for a number of reasons such as capacity and budget constraints. Commitment between partners in the supply chain should be the most priority factor that needs to be strengthened and further developed. A commitment affects not only information sharing but also interpersonal trust [41,111], as well as the relationship between supply chain partners [122]. According to Kwon et al. [123], commitment is one of the main reasons for reducing the disruption of information sharing. Having a good or sustainable relationship makes individuals more willing to communicate more informally with their partners [112]. Commitment significantly boots the development of the relationships between interorganizational in the supply chain [122]. In addition, commitment has a positive relationship with trust [123]. In the other words, the trust is significantly strengthened by the commitment between supply chain partners. This also leads to a long-term relationship between partners in the supply chain.
For the global supply chain, our research findings are fundamental to encourage consideration: commitment, trust, and technology in sharing information. In fact, one of these factors is also introduced in a number of studies related to global supply chains. For example, Arnold et al. [30] examined the relationship between commitment and information sharing in the global supply chain. Shore [124] found that technology affects information sharing in global supply chain. Ueltschy et al. [125] evidence that commitment has a positive effect on the relationships in the global supply chain. However, there are some differences between the global supply chain and the local supply chain. A global supply chain is known as a network that includes facilities across many different countries. It was formed for the purpose of providing goods and services [126]. Therefore, the effect of each factor on information sharing may be reordered in the global supply chain.
Our study contributes two main findings to literature in the field of supply chain information sharing. Firstly, our study provides useful evidence to confirm that commitment plays a key role in information sharing. Thus, commitment should be established as a priority when individuals want to build or improve their information-sharing system/network. In addition, there is about 50% simultaneous influence of other factors on information sharing besides the four factors considered in our study. This can be proposed as a future research direction.
Similar to other studies, our study also has several limitations. The first is input data. Due to the application of meta-analysis, our data is collected from available publications. Thus, although suitable publications are searched and identified carefully, it is still possible that some studies have been missed. Based on the fail-safe number test, however, our observations are enough to provide reliable results. Another is that our study just considers the effect of the most common factors. Hence, some more important factors may be missed.
From limitations in our study, some future directions are proposed. Researchers should extent the research scope by finding the influence of many other factors on information sharing. Then, the future results may compare to our results to find the most important effects on information sharing. These may support managers to limit resource waste for improving many factors instead of the most important factor. In addition, the number of samples should be added to further clarify the relationships between factors and information sharing.