I had heard a while back that the typical turnaround time for a Bay Area based Software Engineer in a startup averages 6-9 months. I feel like, according to anecdotal evidence, this has been somewhat accurate for myself and other people I have worked with -- why stick around when you can hop over to the next company and get a 5-15 percent pay raise? I realized, though, that I didn't have any hard data to back this up. Googling around seems to only come up with results in percentage of attrition rates, but with no timeframes associated with that data. Are there any studies out there that address this topic?