Congressional Research Service. January 6, 2012.
The financial crisis of 2007-2009 and the subsequent economic recession led to large federal deficits that accelerated the growth of total debt, which necessitated a series of debt limit increases. Past experience suggests that direct fiscal costs of a financial crisis, such as costs of bailing out financial institutions, is dwarfed by the effects of diminished tax revenues and elevated social safety net benefits. Debate during the 2011 debt limit episode reflected a growing concern with the fiscal sustainability. Over the next decade, without major changes in federal policies, persistent and possibly growing deficits, along with the ongoing growth in the debt holdings of government accounts, would increase substantially the amount of federal debt subject to limit. Unless federal policies change, Congress would repeatedly face demands to raise the debt limit to accommodate the growing federal debt in order to provide the government with the means to meet its financial obligations.
http://www.fas.org/sgp/crs/misc/RL31967.pdf [PDF format, 35 pages].