1. Within countries, self-reported well-being seems to scale logarithmically of average income. (Again, that means that each doubling of income corresponds to the same, constant increase in reported happiness points.)
2. Between countries, a similar relationship seems to hold.
3. Within countries, per capita GDP growth does not appear to lead to corresponding increases in well-being.
The 3rd claim is controversial. Some researchers (such as Justin Wolfers) have data which suggest that GDP growth does translate into increased well-being, on average. Others like Easterlin have data that seem consistent with the 3rd claim. It’s harder to get a clear empirical answer to it than to the first 2, because it involves a much smaller sample size than claim 1 (one data point per country instead of one data point per person) and a much narrower range of incomes than claim 2 (perhaps 1 doubling of income for a single country over a few decades, versus more like 5 doublings between a poor country and a rich country).
The 3rd claim is controversial. Some researchers (such as Justin Wolfers) have data which suggest that GDP growth does translate into increased well-being, on average. Others like Easterlin have data that seem consistent with the 3rd claim. It’s harder to get a clear empirical answer to it than to the first 2, because it involves a much smaller sample size than claim 1 (one data point per country instead of one data point per person) and a much narrower range of incomes than claim 2 (perhaps 1 doubling of income for a single country over a few decades, versus more like 5 doublings between a poor country and a rich country).