Wealth doesn't matter in itself as much as the distribution of total wealth (and relative wealth). Humans are social animals, they don't just want something to munch and some cover over their head (not to mention that millions don't even have those), they want to do at least as good as what's perceived as average for their society.
If that's truly the case, then all societies everywhere have a permanent and insurmountable Lake Woebegone ( where all the children are above average ) problem.
I don't see how. For one, "at least as good as what's perceived as average for their society" is totally feasible without everybody being "above average".
Second, even that was meant as the thing people strive for and want to have. That doesn't mean that they are only satisfied if they accomplish it and then some, they can also be ok with being below, but close, to the average.
But even more importantly, the key word is "perceived average". They want to be close to what they consider average ("middle class") family lifestyle at least. Not necessarily close to its absolute mathematical definition.
What are you referring to? If you mean economics, the major democracies are wealthier than ever.