"According to CPS data, men 65 to 69 were about six percentage points less likely to be retired in 2004 than in 1992. CPS and Health and Retirement Study (HRS) data indicate a corresponding difference of 3 percentage points between 1998 and 2004. Simulations with a structural retirement model suggest changes in Social Security rules between 1992 and 2004 increased full time work of 65 to 67 year old married men by a little under 2 percentage points, about a 9 percent increase, and increased their labor force participation by between 1.4 and 2.2 percentage points, or 2 to 4 percent, depending on age. Social Security changes account for about one sixth of the increase in labor force participation between 1998 and 2004, for married men ages 65 to 67. These rule changes encourage deferring retirement from long term jobs, returning to full time work after retiring, and increasing partial retirement. Although married men in their fifties decrease their participation in the labor force over this period, this is not due to changes in Social Security, but may reflect other factors, including changes in disability"--National Bureau of Economic Research web site.