Another point of reference: here are some offers recently aggregated on Blind. In 2019, I got an offer almost identical to one of those listed below, and a friend got an offer a little higher than listed below. So I believe the reports are legit.
While the raw salary data on levels.fyi is useful, other context about the candidate & team is pretty important. For example, my friend has no college degree but matched to a very profitable / well-funded team, so he got a relatively larger stock award. levels.fyi probably has a pretty good estimate of how each company assigns base salary bands to the now "standard" four levels (junior, senior, staff, decorated).
It seems sign-on bonuses grew a lot in 2019. Several posts for Facebook new grads getting $100k sign-on bonus.
LinkedIn
Senior
* 185 base, 10% bonus, 300k - 400k for 4 years stock, 60k sign on
* Total Comp: 294 - 319 / yr
Staff:
* 210 base, 15% bonus, 600k for 4 years stock, 75k sign on
* Total Comp: 411 / yr
Senior Staff:
* 230 base, 20% bonus, 1M for 4 years stock, 100k sign on
* Total Comp: 551 / yr
Facebook
Senior:
* 210 base, 15% bonus, 700k for 4 years stock, 80k sign on
* Total Comp: 437 / yr
Staff
* 225 base, 20% bonus, 1.1M for 4 years stocks, 100k sign on
* Total Comp: 570 / yr
Google
Senior
* 195 base, 15% bonus, 750k for 4 years stock, 100k sign on
* Total Comp: 438 / yr
Staff
* 220 base, 20% bonus, 1M for 4 years stock, 120k sign on
* Total Comp: 544 / yr