I believe one aspect of Earning to Give which is understudied and would have significant impacts on these calculations, is the long term viability of giving rates on an individual level. The earning to give strategy necessarily places altruistic people in the midst of largely non-like minded individuals for decades at a time. In what world do we not think this will have an effect on the working givers? To not consider defection rates is naive at best and sloppy science at worst.