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).
I'm currently working on an article about QALYs per life saved (effectivealtruism.org), which would include measurements and a bunch of different values (e.g. 1 USD given to GWWC is [x] lives saved, [y] QALYs, etc). This might be relevant