TIOBE
Frequency: Monthly.
Methodology: Based on the number of queries in popular search engines such as Google, Bing, Yahoo, Wikipedia, Amazon, YouTube, and Baidu using the +“<language> programming” search term.
Redmonk
Frequency: Semi-annually.
Methodology: Based on raw lines of code in GitHub repositories and StackOverflow language tags.
Octoverse.GitHub
Frequency: Annually.
Methodology: Based on the number of opened GitHub pull requests in the past 12 months.
IEEE Spectrum
Frequency: Annually.
Methodology: The rankings are synthesized from 10 sources (Google search of “X programming”; Google Trends; Twitter; GitHub; StackOverflow; Reddit; Hacker News; CareerBuilder; Dice; IEEE Xplore Digital Library).
PYPL
Frequency: Monthly.
Methodology: Based on Google Trends for the “<language> tutorial” search term.
Eng Language Index
Methodology: An extension of PYPL to include missing languages and correct for Objective-C. Found on my Medium blog. (Note: PYPL have since corrected their list for some missing languages, but their data point for Go language appears to be anomalous and Objective-C is still incorrect. I believe PYPL are using the search term “golang tutorial” for Go. This is why its ranking is anomalous. Golang is not the proper name for the Go language.)
CodeEval
Frequency: Annually.
Methodology: Based on 1,200,000+ CodeEval challenge submissions for the year.
HackerRank
Methodology: Languages employers are proactively seeking based on a study of over 3,000 coding interview challenges.
StackOverflow Developer Survey
Frequency: Annually.
Methodology: 56,033 coders in 173 countries surveyed for 2016.
Trendy Skills
Frequency: Irregular.
Methodology: Languages in demand from “major job advertisement websites (e.g., Monster.com and similar)” including countries such as the USA, UK, Germany, Sweden, Spain, Ireland, Netherlands, Austria, Czech Republic, Belgium, Finland, India, and Greece.
Coding Dojo
Methodology: Languages ranked by the number of programming jobs at Indeed.com (The largest job posting aggregator in the US).
New Relic
Methodology: Languages mentioned in the job listings at Indeed.com.