HDI and others were created because it was said that GDP per capita was not measuring happiness well enough, and was too economic. But now we realize they are

HDI and others were created because it was said that GDP per capita was not measuring happiness well enough, and was too economic. But now we realize they are correlated, which begs the questions : are the parts about education, healthcare etc. within the HDI so unimportants ? (ie why did bother creating the HDI if GDP/capita works just as well on most cases) But if works so well, shouldn't we also see diminishing marginal returns in GDP per capita ? (in neoclassical theory, diminishing marginal returns are everywhere !) Some studies have added ad-hoc trigger points (up to $75k and you'll be happy, then not so much) but still from what I get it's a weird situation, and we are still learning important facts about the utility of money. It's quite interesting. EDIT: Marking normative suggestions with regards to GDP per capita - I don't think I would, cause that's quite a bit off my league. There are different models, and many variables - not one simple solution.