I agree with you entirely that if you're trying to measure how well off the majority of Americans as opposed to, say, Swiss, you should look at median income st

I agree with you entirely that if you're trying to measure how well off the majority of Americans as opposed to, say, Swiss, you should look at median income statistics as a much better measure. However, well-off-ness isn't what GDP per capita (PPP or otherwise) is trying to measure. On a side note the best measure of income inequality is the GINI index. The US GINI index is an abysmal 45, contrasted to 33.7 for Switzerland. But, China's is 48 which is staggeringly high for a nominally socialist country.