[Question] What are some key numbers that (almost) every EA should know?

I think it might be interesting and valuable to create a “list of numbers every EA should know”, in a similar vein to Latency Numbers Every Programmer Should Know and Key Numbers for Cell Biologists.

I was originally thinking of either a) making the whole list myself, or b) convincing someone else (eg, an RP intern) to do it, but on AaronGertler’s advice I decided to turn to the Forum to help with crowdsourcing this problem.

We can use upvotes/​downvotes and comments to debate which numbers should be worth including/​excluding.

So what are some key numbers that (almost) every EA should know?

Feel free to answer with either important numbers that you think are cause-specific (eg, numbers of chickens currently alive in factory farms, Toby Ord’s x-risk estimates, extreme poverty rates in 1950 vs 2018) or relatively cause agnostic (eg, $billions that Open Phil has, expected lifespan of social movements, number of atoms in the observable universe).