  Many interventions in global health save lives. One criticism sometimes
lobbed at these interventions invokes the spirit of Malthus. The good done, the
charge goes, is offset by the harm of spreading the earth's limited resources
more thinly: more people, and more misery per person. To the extent this holds,
the net benefit of savings lives is lower than it appears at first. On the
other hand, if lower mortality, especially in childhood, leads families to have
fewer children, life-saving interventions could reduce population. This
document critically reviews the evidence. It finds that the impact of
life-saving interventions on fertility and population growth varies by context,
and is rarely greater than 1:1. In places where lifetime births/woman has been
converging to 2 or lower, saving one child's life should lead parents to avert
a birth they would otherwise have. The impact of mortality drops on fertility
will be nearly 1:1, so population growth will hardly change. In the
increasingly exceptional locales where couples appear not to limit fertility
much, such as Niger and Mali, the impact of saving a life on total births will
be smaller, and may come about mainly through the biological channel of
lactational amenorrhea. Here, mortality-drop-fertility-drop ratios of 1:0.5 and
1:0.33 appear more plausible. But in the long-term, it would be surprising if
these few countries do not join the rest of the world in the transition to
lower and more intentionally controlled fertility.
