I don’t know why but I usually think in terms of cost per unit good, not good per unit cost. I said “1% future-improvement per $5B” but I really think like “$5B per 1% future-improvement.”
These two old GWWC posts (1, 2) argue for using good per unit cost since that’s arithmetically more convenient/intuitive in relevant scenarios. Most relevant excerpts below:
[Unlike consumers making day-to-day purchases (e.g. when you want to buy exactly one chocolate bar, and you are interested in comparing how much money you can save by choosing between various shops),] donors are usually interested in the differences in how much good they can do with a given amount of money, rather than the differences in how much money they can save for a given amount of good they want to do.
And:
What the considerations in post I and this post suggest is that it is usually wise to report cost-effectiveness in terms of DALY/$ rather than $/DALY, because then
the comparison of differences in cost-effectiveness that we care about are more conspicuous, as the differences could be obtained by simple subtraction and;
the most often relevant averages of cost-effectiveness could be reached simply by taking the familiar arithmetic mean, rather than the more cumbersome harmonic mean.
These two old GWWC posts (1, 2) argue for using good per unit cost since that’s arithmetically more convenient/intuitive in relevant scenarios. Most relevant excerpts below:
And: