Yep. The attrition rate is not even remotely close to 50%. My recollection was that this turnover rumor started with a stat that at one point in Google's recent

Yep. The attrition rate is not even remotely close to 50%. My recollection was that this turnover rumor started with a stat that at one point in Google's recent growth, the median tenure of the employees was only 2 years. This stat then got interpreted (and then reported) by some as Google having an obscenely high turnover. Of course, you can't get turnover rate from median tenure, they're completely different things. If the size of a company doubles in a year, the median tenure will be <=1yr. If the most junior employees of another company start quitting en mass, the median tenure for the remaining employees will actually increase. Median tenure is a completely useless in determining how many people are leaving a company.