Software engineer at Wave (https://www.wave.com/en/)
Yeah good point, I'll try to figure out something less rough.
The main source of inaccuracy is that I'm not sure what the right counterfactual is for someone doing a Wave payment. It's probably some proportion of each of: not doing the transfer at all, using some informal method, and using our main comptetitor. For simplicity in my estimate I just assumed that all transfers would have been done using our competitor.