Numbeo

Numbeo is a crowd-sourced global database of reported consumer prices, perceived crime rates, quality of health care, among other statistics.
Description.
Numbeo is a collaborative online database which enables users to share and compare information about the cost of living between countries and cities. The Numbeo website is operated by Numbeo doo, company registered in Serbia. The founder of Numbeo is an ex-Google software engineer.
History.
Numbeo was founded in April 2009 by Mladen Adamovic. Originally it was a website for crowd-sourced price comparison, but later in 2011 it started to collect data about crime, pollution, health care, and traffic.
Popularity.
Numbeo was mentioned or used as a source in hundreds of major newspapers around the world, including "Forbes", "Business Insider", "Time", "The Economist", "BBC", "The New York Times", "China Daily", "The Telegraph". Numbeo claims to be the biggest website of its kind with more than 1.3 million data points collected as of August 2014. According to Alexa's ranking in August 2014, Numbeo.com was among the top 10,000 websites (ranked by traffic).
Numbeo has been sometimes used by UN FAO, IMF, The World Bank and many other international organizations. 
Criticism.
In 2012, Columnist Alistair Walsh suggested in an article written for the website Property Observer, that Numbeo's information is based on what people say and should be taken with grain of salt. There is no third party check or audit on the accuracy of data. 
Comparison against other international city data sources conducted by Ray Woodcock in 2017 suggested that Numbeo might be inaccurate on a city level, while on a country level it is more accurate.