I'm looking for references on population ethics, preferably those with a mathematical bent. Broome's Weighing Lives is a good example of what I'm looking for.
I found that Diamond and Koopmans have booth done some interesting work in this area. The blog post Kill the young people has a discussion of Diamond's paper, and Koopmans' "Stationary Ordinal Utility and Impatience" can be found here.
Basically, they investigate the idea of "impatience" (valuing things which come earlier more) and show that under some reasonable conditions, population ethics must be impatient, a very counter-intuitive finding. It is often mentioned in the context of environmental ethics.