O’Reilly have published their 2015 Data Science Salary Survey.
SQL, Excel, R and Python remain the top tools. Spark (and, consequently, Scala) have been the big climbers—and people with these skills are getting paid well.
R remains popular, but might be an intermediate step to other tools. Those using Python and Spark are less likely to use R. This makes intuitive sense. R is a great statistical analysis tool, but developers tend to prefer more traditional software development languages. If you’ve invested in learning an “enterprise” development language you are likely to stick with it.