​The 2015 Online Marketing Industry Survey - Moz

This year, over 3,600 brave souls, each one more intelligent and good-looking than the last, completed our survey. 

Almost half (49%) of our 2015 respondents involved in search marketing were in-house marketers. In-house teams still tend to be small – 71% of our in-house marketers reported only 1-3 people in their company being involved in search marketing at least quarter-time.  

https://moz.com/blog/2015-online-marketing-industry-survey