2007 OASDI Trustees Report

VI. APPENDICES

D. LONG-RANGE SENSITIVITY ANALYSIS

This appendix presents estimates which illustrate the sensitivity of the long-range actuarial status of the OASDI program to changes in selected individual assumptions. The estimates based on the three alternative sets of assumptions (see sections IV.B, V.A, V.B, and V.C) illustrate the effects of varying all of the principal assumptions simultaneously in order to portray a generally more optimistic or pessimistic future, in terms of the financial status of the OASDI program. In the sensitivity analysis presented in this appendix, the intermediate alternative II projection is used as the reference point, and one assumption at a time is varied within that alternative. The variation used for each individual assumption reflects the levels used for that assumption in the low cost alternative I and high cost alternative III projections. Similar variations in the selected assumptions within the other alternatives would result in similar relative variations in the long-range estimates.

Each table in this section shows the effects of changing a particular assumption on the OASDI summarized income rates, summarized cost rates, and actuarial balances for 25-year, 50-year, and 75-year valuation periods. Because the annual payroll tax rate is constant for the entire 75-year valuation period, the income rate varies only slightly with changes in assumptions and, therefore, is not considered in the discussion of the tables. The change in each of the actuarial balances is approximately equal to the change in the corresponding cost rate, but in the opposite direction.

1. Total Fertility Rate

Table VI.D1 shows the estimated OASDI income rates, cost rates, and actuarial balances, on the basis of alternative II with various assumptions about the ultimate total fertility rate. These assumptions are that the ultimate total fertility rate will be 1.7, 2.0, and 2.3 children per woman as assumed for alternatives III, II, and I, respectively. The rate is assumed to change gradually from its current level and to reach the various ultimate values in 2031.

For the 25-year period, the cost rate for the three fertility assumptions varies by only about 0.05 percent of taxable payroll. In contrast, the 75-year cost rate varies over a wide range, decreasing from 16.25 to 15.51 percent, as the assumed ultimate total fertility rate increases from 1.7 to 2.3. Similarly, while the 25-year actuarial balance varies by only 0.05 percent of taxable payroll, the 75-year actuarial balance varies over a much wider range, from -2.29 to -1.63 percent.

During the 25-year period, the very slight increases in the working population resulting from increases in fertility are more than offset by decreases in the female labor force and increases in the number of child beneficiaries. Hence, the program cost slightly increases with higher fertility. For the 75-year long-range period, however, changes in fertility have a relatively greater impact on the labor force than on the beneficiary population. As a result, an increase in fertility significantly reduces the cost rate. Each increase of 0.1 in the ultimate total fertility rate increases the long-range actuarial balance by about 0.11 percent of taxable payroll.

2. Death Rates

Table VI.D2 shows the estimated OASDI income rates, cost rates, and actuarial balances, on the basis of alternative II with various assumptions about future reductions in death rates for the period 2006-81. These assumptions are the same as those used for alternatives I, II, and III, which are described in section V.A.2. The age-sex-adjusted death rates decline at average annual rates of 0.30 percent, 0.71 percent, and 1.26 percent for alternatives I, II, and III, respectively.

The variation in cost for the 25-year period is less pronounced than the variation for the 75-year period because the decreases in death rates are assumed to occur gradually. The 25-year cost rate increases from 13.97 percent (for an average annual death-rate reduction of 0.30 percent) to 14.30 percent (for an average annual death-rate reduction of 1.26 percent). The 75-year cost rate increases from 15.26 to 16.60 percent. The actuarial balance decreases from +0.73 to +0.40 percent for the 25-year period, and from -1.36 to -2.65 percent for the 75-year period.

Lower death rates cause both the income (through increased taxable payroll) and the cost of the OASDI program to be higher than they would otherwise be. The relative increase in cost, however, exceeds the relative increase in taxable payroll. For any given year, reductions in the death rates for people who are age 62 and over (ages at which death rates are the highest) increase the number of retired-worker beneficiaries (and, therefore, the amount of retirement benefits paid) without adding significantly to the number of covered workers (and, therefore, to the taxable payroll). Although reductions for people at ages 50 to retirement eligibility age do result in significant increases to the taxable payroll, those increases are not large enough to offset the sum of the additional retirement benefits mentioned above and the disability benefits paid to additional beneficiaries at these pre-retirement ages, which are ages of high disability incidence. At ages under 50, death rates are so low that even substantial reductions would not result in significant increases in the numbers of covered workers or beneficiaries. Consequently, if death rates for all ages are lowered by about the same relative amount, cost increases at a rate greater than the rate of growth in payroll, thereby resulting in higher cost rates and, therefore, lower actuarial balances. Each additional 0.1-percentage-point reduction in the average annual death-rate reduction decreases the long-range actuarial balance by about 0.13 percent of taxable payroll.

3. Net Immigration

Table VI.D3 shows the estimated OASDI income rates, cost rates, and actuarial balances, under alternative II with various assumptions about the magnitude of net immigration. These assumptions are that the annual net immigration will be 672,500 persons, 900,000 persons, and 1,300,000 persons as assumed for alternatives III, II, and I, respectively.

For all three periods, the cost rate decreases with increasing rates of net immigration. For the 25-year period, the cost rate decreases from 14.26 percent of taxable payroll (for annual net immigration of 672,500 persons) to 13.96 percent (for annual net immigration of 1,300,000 persons). For the 50-year period, it decreases from 15.53 percent to 15.05 percent, and for the 75-year period, it decreases from 16.09 percent to 15.57 percent. The actuarial balance increases from +0.47 to +0.70 percent for the 25-year period, from -1.40 to -1.00 percent for the 50-year period, and from -2.14 to -1.70 percent for the 75-year period.

The cost rate decreases with increasing rates of net immigration because immigration occurs at relatively young ages, thereby increasing the numbers of covered workers earlier than the numbers of beneficiaries. Each additional 100,000 net immigrants increases the long-range actuarial balance by about 0.07 percent of taxable payroll.

4. Real-Wage Differential

Table VI.D4 shows the estimated OASDI income rates, cost rates, and actuarial balances, on the basis of alternative II with various assumptions about the real-wage differential. These assumptions are that the ultimate real-wage differential will be 0.6 percentage point, 1.1 percentage points, and 1.6 percentage points as assumed for alternatives III, II, and I, respectively. In each case, the ultimate annual increase in the CPI is assumed to be 2.8 percent (as assumed for alternative II), yielding ultimate percentage increases in average annual wages in covered employment of 3.4, 3.9, and 4.4 percent.

For the 25-year period, the cost rate decreases from 14.57 percent (for a real-wage differential of 0.6 percentage point) to 13.71 percent (for a differential of 1.6 percentage points). For the 50-year period, it decreases from 15.98 to 14.69 percent, and for the 75-year period it decreases from 16.58 to 15.18 percent. The actuarial balance increases from +0.24 to +0.89 percent for the 25-year period, from -1.75 to -0.72 percent for the 50-year period, and from -2.51 to -1.40 percent for the 75-year period.

The cost rate decreases with increasing real-wage differentials. This is because higher wages increase taxable payroll immediately, but increase benefit levels only gradually as new beneficiaries become entitled. In addition, cost-of-living adjustments (COLAs) to benefits are not affected by changes in wages, but only in prices. Each 0.5-percentage-point increase in the assumed real-wage differential increases the long-range actuarial balance by about 0.56 percent of taxable payroll.

5. Consumer Price Index

Table VI.D5 shows the estimated OASDI income rates, cost rates, and actuarial balances, on the basis of alternative II with various assumptions about the rate of increase for the Consumer Price Index (CPI). These assumptions are that the ultimate annual increase in the CPI will be 1.8 percent, 2.8 percent, and 3.8 percent as assumed for alternatives I, II, and III, respectively. In each case, the ultimate real-wage differential is assumed to be 1.1 percentage points (as assumed for alternative II), yielding ultimate percentage increases in average annual wages in covered employment of 2.9, 3.9, and 4.9 percent.

For all three periods, the cost rate decreases with greater assumed rates of increase in the CPI. For the 25-year period, the cost rate decreases from 14.29 (for CPI increases of 1.8 percent) to 13.98 percent (for CPI increases of 3.8 percent). For the 50-year period, it decreases from 15.55 to 15.12 percent, and for the 75-year period, it decreases from 16.12 to 15.64 percent. The actuarial balance increases from +0.45 to +0.68 percent for the 25-year period, from -1.42 to -1.05 percent for the 50-year period, and from -2.17 to -1.74 percent for the 75-year period.

The patterns described above result primarily from the time lag between the effects of the CPI changes on taxable payroll and on benefit payments. When assuming a greater rate of increase in the CPI (in combination with a constant real-wage differential), the effect on taxable payroll due to a greater rate of increase in average wages is experienced immediately, while the effect on benefits due to a larger COLA is experienced with a lag of about 1 year. Thus, the higher taxable payrolls have a stronger effect than the higher benefits, thereby resulting in lower cost rates. The effect of each 1.0-percentage-point increase in the rate of change assumed for the CPI is an increase in the long-range actuarial balance of about 0.22 percent of taxable payroll.

6. Real Interest Rate

Table VI.D6 shows the estimated OASDI income rates, cost rates, and actuarial balances, on the basis of alternative II with various assumptions about the annual real interest rate for special public-debt obligations issuable to the trust funds, which are compounded semiannually. These assumptions are that the ultimate annual real interest rate will be 2.1 percent, 2.9 percent, and 3.6 percent as assumed for alternatives III, II, and I, respectively. In each case, the ultimate annual increase in the CPI is assumed to be 2.8 percent (as assumed for alternative II), resulting in ultimate annual yields of 5.0, 5.8, and 6.5 percent.

For the 25-year period, the cost rate decreases slightly with increasing real interest rates from 14.29 percent (for an ultimate real interest rate of 2.1 percent) to 14.01 percent (for an ultimate real interest rate of 3.6 percent). For the 50-year period, it decreases from 15.61 to 15.09 percent, and for the 75-year period, it decreases from 16.26 to 15.55 percent. The actuarial balance increases from +0.32 to +0.78 percent for the 25-year period, from -1.63 to -0.88 percent for the 50-year period, and from -2.47 to -1.50 percent for the 75-year period. Each 0.5-percentage-point increase in the assumed real interest rate increases the long-range actuarial balance by about 0.32 percent of taxable payroll.

7. Disability Incidence Rates

Table VI.D7 shows the estimated OASDI income rates, cost rates, and actuarial balances, on the basis of alternative II with various assumptions concerning future disability incidence rates. For all three alternatives, incidence rates by age and sex are assumed to vary during the early years of the projection period before attaining ultimate levels in 2027. In comparison to the corresponding annual rates experienced during the base period 1994-96, the ultimate age-sex-adjusted incidence rate is 2 percent higher for alternative II, 19 percent lower for alternative I, and 22 percent higher for alternative III.

For the 25-year period, the cost rate increases with increasing disability incidence rates from 13.97 percent (for the relatively low rates assumed for alternative I) to 14.39 percent (for the relatively high rates assumed for alternative III). For the 50-year period, it increases from 15.09 to 15.61 percent, and for the 75-year period, it increases from 15.62 to 16.17 percent. The actuarial balance decreases from +0.73 to +0.32 percent for the 25-year period, from -1.00 to -1.51 percent for the 50-year period, and from -1.70 to -2.24 percent for the 75-year period.

8. Disability Termination Rates

Table VI.D8 shows the estimated OASDI income rates, cost rates, and actuarial balances, on the basis of alternative II with various assumptions about future disability termination rates. For all three alternatives, deaths rates are assumed to decline throughout the long-range period. For alternative II, the age-sex-adjusted¹ death rate is assumed to decline to a level at the end of the 75-year period that is about 47 percent lower than the level in 2006. For alternative I, the age-sex-adjusted death rate is assumed to decline to a level at the end of the 75-year period that is about 22 percent lower than the level in 2006. For alternative III, the age-sex-adjusted death rate is assumed to decline to a level at the end of the 75-year period that is about 71 percent lower than the level in 2006.

For all three alternatives, ultimate recovery-termination rates by age, sex, and duration are assumed to be attained in the twentieth year of the projection period. For alternative II, the age-sex-adjusted1 recovery rate in 2026 is about 10 recoveries per thousand disabled-worker beneficiaries. For alternative I, the age-sex-adjusted recovery rate in 2026 is about 11 recoveries per thousand disabled worker beneficiaries. For alternative III, the age-sex-adjusted recovery rate in 2026 is about 8 recoveries per thousand disabled-worker beneficiaries.

For the 25-year period, the cost rate increases with decreasing disability termination rates from 14.09 percent (for the relatively high rates assumed for alternative I) to 14.17 percent (for the relatively low rates assumed for alternative III). For the 50-year period, it increases from 15.28 to 15.37 percent, and for the 75-year period, it increases from 15.83 to 15.91 percent. The actuarial balance decreases from +0.61 to +0.53 percent for the 25-year period, from -1.19 to -1.27 percent for the 50-year period, and from -1.91 to -1.99 percent for the 75-year period.

¹ Age adjusted to the total disabled workers in current-pay as of January 1, 2000.