It's pretty simple to get a rough estimate of how many people you need to hire a year. You take your engineering count, say ~10,000, how long engineers stay at

It's pretty simple to get a rough estimate of how many people you need to hire a year. You take your engineering count, say ~10,000, how long engineers stay at each company, say 4 years, and you come out to 2,500 engineers you need to hire every year, assuming you don't need to grow, to maintain the status quo. So then you take a larger company like google, with ~100,000 engineers, and they'll need to hire at least 25,000 engineers a year.