""The Grant Study is an 87-year continuing longitudinal study from the Study of Adult Development at Harvard Medical School, started in 1938.[2] It has followed 268 Harvard-educated men, the majority of whom were members of the undergraduate classes of 1942, 1943 and 1944.""
So they took the cream of the crop in the US and tracked it for 80 years. Most of these people will never starve or have to choose a tier 3 education for their children. It's useful as a study, but mostly to demonstrate what matters for the affluent / well-off for their happiness.