Typical AP propaganda piece...they wouldn't dare break down the figures of WHO got wealthy and WHO didn't.
I would also bet they wouldnt be very quick to break out which contributing factors saw the largest annual increases or decreases. IMHO, the increases are artificial. Artificially induced increases in the stock market are likely the biggest contributing factor, and only to the wealthiest Americans on average.

However, when you use generic information and summarize all the data in the way the AP did, it makes for a really nice feel good piece that I'm certain the Obama administrations news reviewers would approve for publishing.