From a recent report by Social Security's Office of Inspector General (OIG):
Our review of 1,532 beneficiaries in current pay status as of October 2003 found that over a 10-year period (from October 2003 through February 2014), SSA [Social Security Administration] assessed overpayments for 44.5 percent of sampled beneficiaries. Based on the sample, we estimated
SSA assessed overpayments totaling about $16.8 billion between October 2003 and February 2014 for approximately 4 million beneficiaries who were in current payment status in October 2003 ;
SSA recovered about $8 .1 billion of the $16.8 billion in overpayments it assessed ; and
SSA prevented about $8 billion in overpayments between October 2003 and February 2014 to approximately 1 million beneficiaries in current pay status in October 2003 by suspending monthly payments.
Additionally, the overpayment rate in Fiscal Year 2004 was 3.1 percent of all benefits paid that year.The report goes on to note that although it can take time, after ten years Social Security had been able to recover 85% of the overpayments made in 2003. Many of the overpayments were, as the report puts it, unavoidable because the individuals received interim benefits while they appealed benefit terminations.