I am not refuting your point ("money does not happiness make") but AFAIK, it is a known fact that people tend to a state of average happiness no matter what their condition is (e.g. if they lack the ability to walk or if they own private jets).

But there is a correlation between the youth/child death rate and the number of kids, and it can be generally agreed death impairs the pursuit of happiness.

(Though, quite likely child death implies many kids, not the other way around)