See Budget  Prompt Action Necessary to Avert Long-Term Damage to the Economy (GAO/OCG-92-2, June 5, 1992), The Deficit and the  An Update of Long-Term Simulations (GAO/AIMD/OCE-95-119, April 26, 1995), Budget  Deficit Reduction and the Long Term (GAO/T-AIMD-96-66, March 13, 1996), Budget  Analysis of Long-Term Fiscal Outlook (GAO/AIMD/OCE-98-19, October 22, 1997), Budget  Long-Term Fiscal Outlook (GAO/T-AIMD/OCE-98-83, February 25, 1998), Budget  July 2000 Update of GAO's Long-Term Simulations (GAO/AIMD-00-272R, July 26, 2000), and Long-Term Budget  Moving From Balancing the Budget to Balancing Fiscal Risk (GAO-01-385T, February 6, 2001).
Please refer to this list of documents containing pertinent information.