Did you ever run percent when you were there? I started at Google in 2006 and one of the 'fun' things people did was run the 'percent' command that would tell you what percentage of Google employees were 'newer' than you, so if it was 10% you knew that 10% of the people were new. I was curious how it worked and found that it just counted rows in a database that had active employee names and start dates. Pretty simple hack.
The amazing thing was how quickly the number grew! And at TGIF there were the Nooglers in their propeller caps and everyone was like wow look at all those newbies. About 6 months in I noticed two things, first there was like 25% of the company was newer than I was, and that the number of employees being reported in the financial reports was about the same as when I joined. One could do the math. Waves of people would be hired, large chunks of them wouldn't survive the first year, and another chunk wouldn't survive 'slotting'. They were just no longer at the company. After a couple of years, as I remember it there were three of us, out of about 30, from the group that joined when I did, still at the company.
When I looked for it, it was pretty clear there was a tremendous amount of 'churn' in employment. I asked Lazlo Bock about it once, he was heading up 'People Operations' at the time and he assured me there were always plenty of candidates in the pipeline and Google wanted only the best and brightest. The people we had? Well they weren't always a good fit "culturally" with the company, after all Google was unlike any company that had ever existed, right?
It was just one of the more egregious times where the 'actions' and the 'words' didn't actually communicate the same message.