Yeah, it’s an odd measurement. I mainly care because it means we’re superior to tassieburgers :)

Seriously though, it’s meant to measure things like poverty, literacy, unemployment, the things usually deemed essential in western societies. The worldwide chart seems to list the US quite high up though, so I’m not sure it really reflects anything besides “how well developed are rich people in western countries” vs “how undeveloped are the poorest people in the poorest countries”