A recent study by the Pew Research Center found that although the United States has one of the highest rates of income inequality between the rich and the poor in the world, it is also one of the places where people are least outraged by the gap.

The study by Bruce Stokes, Pew's director of global economic attitudes at its Global Attitudes Project, found that although the top 20 percent of U.S. earners make 16.7 times more than what those in the bottom 20 percent make, only 47 percent of all Americans called this gap a "very big problem."

"In most countries, there is a strong correlation between public concern about the rich-poor gap and the underlying economic reality. But in the U.S., compared to the other richest nations surveyed, the correlation between public concern and the size of the gap is much weaker," Stokes wrote.

The country where the fewest people see their income gap as a significant problem is Australia at 33 percent. But in Australia, the wealth difference is much less stark. The top 20 percent there earn only 2.7 times what the bottom 20 percent make.

Elsewhere, strong majorities in countries like France (65 percent), Italy (75 percent), Spain (75 percent) and Greece (84 percent) say the gap is a very big problem. Sentiment is closest to the United States in Britain, where exactly 50 percent say the gap is a problem. In those European countries, the top earners make four to seven times more than the bottom earners.

The difference was starkest in South Africa (70 percent), Brazil (75 percent) and Bolivia (58 percent). the only countries surveyed that had larger income gaps than the United States. In those countries, the top earners make, respectively, 25, 21 and 28 times more than bottom earners.

Of all of the countries surveyed by Pew, only Indonesia (46 percent), Malaysia (41 percent) and Jordan (44 percent) had lower rates of concern than the United States and Australia. Much more typical were countries like Mexico (67 percent), Turkey (68 percent) and Russia (59 percent).

What accounts for this difference? The answer maybe that the United States still maintains one of the world's highest per capita standards of living. This probably goes a long way toward undercutting anger towards the very rich. It certainly stands to reason that anger would be higher in countries where most people are much worse off. In other words, a rising tide really does lift all boats.