Paul Krugman documents and analyzes the growth in inequality in the US, attributing it, rightly in my view, to changes in social attitudes and the distribution of political power rather than to underlying forces. In passing, he notes that median incomes in the US have risen by only 10 per cent in the past 20 years, and demolishes the Instapundit factoid claim that people are better off in Mississippi than in Sweden.
For those who prefer striking examples to statistics, check out the latest from Arianna Huffington