First, median household income in 2007 was a bit over $50k -- http://en.wikipedia....the_United_States -- so $30k is on the lower edge of "middle class".

But the point of that article is that the middle class isn't getting anywhere, while the top few percentiles are getting all the benefits. From '67 to '03 median income (in adjusted dollars) had risen from $33k to $43k -- ~30%. But the income of the 95th percentile had risen from $88k to $154k -- ~75%. http://en.wikipedia....ion_1967-2003.svg

If you look at the chart showing 1947-2007 -- http://en.wikipedia....ion_1947-2007.svg -- you can see that everyone's income improving at about the same rate until about 1970. Then the lower percentiles flatline while the top ones keep going up. And the higher you start, the steeper you keep going up.

So the story isn't about poverty, or welfare, or the exact definition of "middle class". The story is that for the decades after WWII all income groups were benefiting at about the same rate. Then starting in the 70s, the wealthy have been getting wealthier. And the wealthier you are, the more you improve each year.