I agree that it isn’t easy to quantify all of these.
Here is something you could do, which unfortunately does not take into account the changes in charities operation at different times, but is quite easy to do (all of the figures should be in real terms).
Choose a large interval of time (say 1900 to 2020), and at each point (say every month or year), decide how much you invest vs how much you donate, according to your strategy (and others).
Choose a model for how much money you have (for example, starting with a fixed amount, or say receiving a fixed amount every year, or receiving an amount depending on the return on investment in the previous year).
Sum up the total money donated over the course of that interval, and calculate how money you have in the end.
Then, you can compare for different strategies the two values at the end. You can also sum the total donated and the money left, pretending to donate everything left at the end of the interval. Or you could adjust your strategies such that no money is left at the end.
I agree that it isn’t easy to quantify all of these.
Here is something you could do, which unfortunately does not take into account the changes in charities operation at different times, but is quite easy to do (all of the figures should be in real terms).
Choose a large interval of time (say 1900 to 2020), and at each point (say every month or year), decide how much you invest vs how much you donate, according to your strategy (and others).
Choose a model for how much money you have (for example, starting with a fixed amount, or say receiving a fixed amount every year, or receiving an amount depending on the return on investment in the previous year).
Sum up the total money donated over the course of that interval, and calculate how money you have in the end.
Then, you can compare for different strategies the two values at the end. You can also sum the total donated and the money left, pretending to donate everything left at the end of the interval. Or you could adjust your strategies such that no money is left at the end.