Every year the StackOverflow.com website has a poll of software developers. Here are the results for 2017 from 64,000 software developers.

https://insights.stackoverflow.com/survey/2017#overview

They also have made a Salary Calculator to go along with it:

https://stackoverflow.com/jobs/salary?utm_source=Iterable&utm_medium=email&utm_campaign=sal-calc&utm_content=var3