Even with two scheduled increases in the normal retirement age in 2008 and 2026, the Social Security Administration projects that the dependency ratio (the ratio of workers entitled to social security retirement bene ts to those paying payroll taxes) will more than double between 1997 and 2050. Figure 11 shows four projected paths of the dependency ratio, corresponding to alternative eligibility rules: perpetuating the current 65 age quali- cation, adhering to the two legislated postponements to age 66 in 2008 and to age 67 in 2026, adding two additional postponements beyond those two, or with 11 postponements { eventually leaving the retirement eligibility age at 76. The demographic transition will require scal adjustments to nance our unfunded social security system, with one possibility being further increases in the normal retirement age. Although the demographic projections contained in Figure 1 have inspired public discussion of social security reforms, rarely have they been used in general equilibrium computations designed to inform that discussion.