I happened to study this in my History degree back in 1995 (I took 'quantification in history' because I liked math, then utterly sucked at it. But I digress).

Happiness is an extremely tricky subject, and the Latin America thing brought back memories of discussions about whether LA countries and cultures simply self-identified as happy, or whether they really were happier. I always thought just asking people if they were happy was a really dumb way of comparing levels of happiness, and that more objective measures of populations, like number of suicides (however problematic in itself, eg a reluctance in some cultures to identify death as suicide) was more reliable.