Since 2007, the number of people collecting social security disability benefits, or SSDI, has grown by 3.4 million. Two new studies, one co-produced by the Obama administration, document a direct relationship between those seeking SSDI after their unemployment benefits run out. With 10.6 million Americans receiving payments of roughly $1,000 a month plus access to Medicare and Medicaid, there are concerns that the Social Security Trust Fund will be completely depleted by 2017. Mark Duggan is a professor of business and public policy at the Wharton School of Business at the University of Pennsylvania. He has studied the relationship between the unemployment rate and applications for disability benefits.