Giving What We Can recently celebrated its 5th birthday. It's not much of a party if no-one external congratulates you, so here we go: Happy Birthday, GWWC!
It's pretty impressive how much GWWC has grown since those early days. Here's a chart of total membership, which I've put together from GWWC emails and liberal use of the internet archive. I'm sure they have better data (without gaps!) internally, but I've never seen this chart before. Notably, growth seems to have picked up since the fall of 2013. Did GWWC change their strategy at that point? (or their membership-counting-methodology?)
Putting the same chart on a log scale, we can see that GWWC have actually done a reasonably good job of sustaining exponential growth.
Fitting a line of best fit to the chart, I estimate GWWC's membership is growing 73.1% a year. Assuming 2% population growth, it will take just 30.25 years before all the world's population are GWWC members. Taking over the world by the time I'm 58 sounds like pretty good going!
Happy Birthday, Giving What We Can!
edit: formatting of links
Another potential explanation (entirely compatible with the above): Giving What We Can gradually started taking paid staff from the latter half of 2012; this was a big injection in terms of person-hours and money going into GWWC. Between start-up costs and the delay in terms of new initiatives being implemented and people actually joining as a result of those initiatives, the effects of this injection were only felt one year later.
A neutral look at the graph doesn't suggest that - it shows membership growth staying flat for a long time before and after Giving What We Can started taking money, which is at least equally compatible with the hypothesis that that money didn't increase membership. You couldn't say that any increase in membership at any point after this showed otherwise.
What were the new initiatives undertaken halfway through 2012 which plausibly led to more members over a year later?