Read it here, excerpt:
…evidence on earnings mobility in the sense of where parents and children rank suggests that our uniqueness lies in how ineffective we are at lifting up men who were poor as children. In other words, we have no more downward mobility from the middle than other nations, no less upward mobility from the middle, and no less downward mobility from the top. Nor do we have less upward mobility from the bottom among women. Only in terms of low upward mobility from the bottom among men does the U.S. stand out.