NPR: Statistics from Economic Mobility Project at Pew

http://www.npr.org/2013/03/07/173733691/social-mobility-is-the-american-dream-slipping-away

This newscast was very informative; NPR is pretty neutral. 
Research has shown that people who are raised in the top fifth of the income distribution are highly likely to stay there. Data show that 43 percent of people who start at the bottom remain stuck at the bottom. Little less than 60 percent make it up out of the bottom. They don't necessarily make it far. We know 70 percent stay in the bottom two-fifths of the income distribution.