I think you're right that the big shift in income distribution has been driven by widening wage differentials—earnings differentials. If you look at the pay gap between CEOs in the top 300 U.S. companies—and these trends are fairly typical of other countries just a bit more exaggerated—compared to the average production worker, up until about 1980 the CEOs were getting 25 times or 30 times as much as the average production worker. By 2000, or early that decade, they were getting 300 or 400 times as much. This has happened in one country after another. It happened first in English-speaking countries—a little bit later, actually, in Canada—and then it spread to non-English-speaking European countries.
I would just say, though, that when people are talking about economic growth and inequality, there's a lot of research looking at the relationship between equality and growth. Although there are some papers that come down on either side of that, the majority suggest that greater equality is good for growth. That's partly because more unequal societies have lower social cohesion. They have more crime. Kids have lower math and literacy scores. You have more people in prison. You have lower social mobility. You're wasting a lot of your talent where you have great inequality.