The five combined have a total headcount of roughly 660k, meaning they would need to be hiring annually roughly 7.5% of their total just in software engineers.

The five combined have a total headcount of roughly 660k, meaning they would need to be hiring annually roughly 7.5% of their total just in software engineers. At that level I don't buy it. Since the number is dominated by Amazon, who has a huge logistics contingent, I'm not sure specifically about engineers. I'd say roughly half of that total is engineers that have something to do with software (not necessarily software engineers). That bumps your number to over 15% of the total engineering headcount. I'll be conservative and say 25% of the engineers are not software (with most being in Apple and Amazon). Now we're looking at 50k being 19% of the total software engineers. You seem to be talking about hired at all levels, while I was talking about only senior hires. In that case, I am closer to you than I indicated. My (possibly wrong) impression is that the majority of hiring by these companies is new grads and juniors, since that is what their interview processes are heavily biased towards. I put the total number of senior hires at 10k - 15k. As for total hires overall, I'll buy either your total hires or your retention rate, but not both. These companies are not growing headcount fast enough to be doing that much hiring at that retention rate in software engineers alone.