Does the Growing Income Gap Threaten the Middle Class?

In 1915, the top 1% of Americans had 18% of the nation's wealth. Now they have 24%.  That's despite the invention of labor unions, government regulations and the income tax.  Timothy Noah, senior writer for the online magazine Slate.com, has written a 10-part series on income inequality, its effect on the economy and what can be done to reverse the trend.