I generated a graph of the number of EA Forum posts per year, as well as the number of new user registrations. I extracted the data using the GraphQL API.
The raw JSON data for all posts is here. I had to split the user data into two files due to upload limits. The raw JSON data for all unbanned (but otherwise unfiltered) users is here. The JSON data for all banned users is here.
Results:
(The post count includes “meta” posts.)
2011: 1
2012: 7
2013: 66
2014: 234
2015: 460
2016: 296
2017: 285
2018: 442
2019 (so far): 433
New user registrations by month; New user registrations by year. If you include banned users, you get this monstrosity.
I divided the users into four categories in order to try to make the numbers more useful. The year entries below list the frequency values in this order.
unbanned users with non-zero posts/comments and non-negative karma.
unbanned users with non-zero posts/comments and negative karma
unbanned users with zero posts/comments
banned users
That said, the database’s indices for number of posts and number of comments don’t seem to reflect reality perfectly. Take a quick look at this table for what I mean.
Note: A previous version of this comment had different values, because I mistakenly was ignoring users with null-valued karma in the database. Now I just treat them as if they had zero karma.
2014: 336; 7; 186; 1
2015: 284; 9; 538; 1
2016: 188; 36; 540; 3
2017: 224; 70; 617; 7
2018: 366; 43; 746; 21
2019 (so far): 382; 22; 652; 1750
Regarding the Effective Altruism FB group member growth over time, I was able to piece together the following graph using archived snapshots and various other sources: https://i.imgur.com/Lejj0e1.png
The raw data (including sources for each data point) is available here. If anyone has more comprehensive data, please let me know.
Based on that, I estimate (linearly interpolate) the following member counts for January 1 of each year:
2014: ~1905
2015: ~4535
2016: ~8610
2017: ~11983
2018: ~14119
2019: ~16003
You have the actual data for 2018 and 2019. If you could share the correct counts for January 1 of those years it would be nice.