[jmherbener]

It depends on how one defines social mobility and what proxy one uses to indicate its extent. Sowell claims that the standard sociological definition is not the relevant one and suggests replacing it with “economic mobility.”

http://townhall.com/columnists/thomassowell/2013/03/06/economic-mobility-n1525556/page/full

http://cafehayek.com/2007/11/economic-mobili.html

Here is the IRS study on income mobility:

http://www.treasury.gov/resource-center/tax-policy/Documents/incomemobilitystudy03-08revise.pdf

Here is a broader study on income mobility put out by the Boston Fed:

https://www.bostonfed.org/economic/wp/wp2011/wp1110.pdf