Fourth out of 169 (the number of countries surveyed) isn't bad. However, if an index of income inequality is factored in, the U.S. falls to number 12 (of a much smaller total). If gender inequality were factored in we would be even lower (We rank number 37 in sexual equality.) Other indicators are noted (including sustainability, health, press freedom, and communication access. These were mostly beyond my ability to evaluate quickly, But introducing any or all of them would serve only to lower the well being of the people of the United States out of the top ten and perhaps the top twenty. I note that NPR referred to the index as an "index of well being."
In a nation supposedly founded on the principle of equality, we are quite ( i would say shockingly) complacent about the depths to which we will allow people to sink in order to preserve our alleged superiority over them.