This article has an interesting take on rising income inequality in the Western World, with particular focus on the United States.
A couple of points to elaborate on. The study that removes the effect of young and old workers can be read, in plain English, here.
Some interesting conclusions of the article:
A majority of Americans have no credit card debt. And of the 46 percent of Americans who do, the Federal Reserve's Survey of Consumer Finances says the median balance is $2,100. Moreover, Pew surveys from 2004 through 2006 found that only 9 percent of Americans said that they "owed a lot more [in credit card and installment debt] than they could afford."
Middle class assets are up. Real median net worth for all households rose from $69,000 in 1989 to $93,000 in 2004 -- an increase of 35 percent.
Most household debt is mortgage debt. Mortgage debt as a share of total debt has increased from 71 percent in 1989 to 79 percent in 2004. For the vast majority of people, their major source of wealth is equity in their home.
Bankruptcies are rare. Only 1.5 percent of households declare bankruptcy in any given year.
The data on income inequality is also extremely interesting. On the one hand income inequality is most definitely on the rise.
On the other hand, consumption inequality does not look to be rising as fast. (This can be explained by economics using a lifetime earnings model. Since consumers attempt to maximize total consumption over a lifetime, they will often borrow/save in order to smooth their consumption over a period of years, ignoring periodic up/down swings in income. Since the market has become more efficient in allowing this--think Credit Cards, ATM's, ARM Mortgages---it is reasonable to believe that consumption inequality will be less than income inequality).
On the other hand, the rise in income inequality is an interesting phenomenon worth thinking about. In my opinion, the reason is a combination of technological changes and the superstar phenomenon. In other words, technology has amplified the returns to skills of certain performers.
As to the political implications of rising income inequality I am less certain. On the one hand, the Robber Barron's error could cause a large amount of political strife. On other other hand, do you feel more envious of Bill Gates earning USD50bn or the fact that your neighbor just got a raise to USD100 thousand and is now making more than you?
Of course if there was more equality in the education system then income mobility would likely be higher. But that is not the case right now. It is also the case that we could have a more efficient health care system. But that is a a whole other topic and debate.