The article containing all the graphs about income inequality really does tell the story of income inequality over the past few decades, it does bury it a little. The first graph it talks about shows inflation adjusted incomes since the 1980s. Looking at this graph, it appears that the bottom half of the income ladder was stagnant over this period, while the top half's income actually grew, with a drastic increase in the very top percentiles.
This picture is a little bit misleading. To understand why, consider this scenario: two men make deposits at a bank. One man deposits $100, the other deposits $1,000. The men return to their respective bank account in a year and discover they have earned interest; the first man has made $5, while the second man has made $50. So who made more money? Clearly, the second man made more dollars than the first did in interest, but the rate of return was exactly the same for both of them.
If we zoom in on the graph they give us, we can see a similar picture. From roughly 1982 until 2000, incomes rose across all income brackets (including the bottom five percent). After 2000, however, most brackets' incomes begin to fall, except for the very top income brackets, which remain stagnant. Due to the scale of small incomes relative to large incomes, however, it is difficult to see anything but the change in large incomes.
Why this occurred is an entirely different issue which I'm sure we will all debate on Wednesday, but I would credit the "boom" years from 82-2000 to Reagan (in part) and credit the 2000-present tragedy to Alan Greenspan (and his mindless minion, Ben Bernanke).