Unfortunately US is consistently ranked something like 32 or 33 out of 36 for inequality across population for countries in the OECD index. Basically Mexico, Chile, and Brazil are outliers by an order of magnitude and US trades spots among Turkey and Russia year to year, then every other country does better. It's also notable that of your examples all are better with Norway, Sweden, and Finland particularly good. Furthermore the OECD household net-adjusted disposable income does not subtract expenditures it probably should, for example not all of the medical costs. I have been averaging $13000 for one child alone over the last two years in expenditures that the formula does not consider. The year before that there was even more for my wife. In a household of five it adds up and there seems to be one outlier needing more medical care than the rest.