Short-Range Actuarial Projections of the Old-Age, Survivors, and Disability Insurance Program, 2001
Actuarial Study No. 115
Chris Motsiopoulos and Tim Zayatz, A.S.A.
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Appendix

C. DISABLED WORKER ADJUSTED INCIDENCE RATE

Shifts in the age and gender composition of the insured population occur over time. To compare disability incidence rates for different years, we need to eliminate the distortions caused by these shifts. For this reason, gross incidence rates are adjusted to provide a measure of the rate at which individuals are being awarded that is independent of demographic shifts. The short-range model performs the adjustment using direct standardization on 5-year age groups. Sample calculations of gross and age-adjusted incidence rates are presented below.

Gross Rate

The gross incidence rate for a particular year is simply total awards divided by exposure for that year. The following table is used to calculate the gross incidence rate for male disabled workers for calendar year 2010. Dividing total awards of 466,007 by the year's exposure of 78,088,156 life-years gives a gross incidence rate of 5.97 awards per thousand exposed.

  Age
  Male disability insured
aggregate years exposed
for calendar year 2010
  Projected
male incidence rate
for calendar year 2010
(per thousand)
 
Male awards
for calendar year 2010
based on 2010 exposure
15-19
1,879,004
0.43
815
20-24
8,369,469
1.30
10,868
25-29
9,306,644
1.53
14,239
30-34
8,477,048
1.83
15,506
35-39
8,101,774
2.67
21,672
40-44
8,665,303
3.69
31,947
45-49
9,424,329
5.01
47,229
50-54
9,180,081
8.12
74,510
55-59
7,609,412
14.05
106,878
60-64
5,892,703
21.80
128,432
65-NRA
1,182,386
11.77
13,911
Total
78,088,156

466,007

Age-Adjusted Rate

The age-adjusted incidence rate for a particular year is computed as total "adjusted" awards divided by the exposure for the standard year. Adjusted awards represent the number that would occur in a particular year if the insured population had the same age-specific profile as the insured population for the standard year. The following table is used to calculate the age-adjusted incidence rate for male disabled workers for calendar year 2010. Dividing total adjusted awards of 348,265 by 1998 exposure of 69,306,132 life-years gives an age-adjusted incidence rate of 5.03 awards per thousand exposed.

  Age
 
Male disability insured
aggregate years exposed
for calendar year 1998
  Projected
male incidence rate
for calendar year 2010
(per thousand)
  Male adjusted awards
for calendar year 2010
based on 1998 exposure
15-19
1,660,415
0.43
720
20-24
6,788,708
1.30
8,815
25-29
8,396,971
1.53
12,847
30-34
9,021,285
1.83
16,502
35-39
10,088,297
2.67
26,986
40-44
9,572,227
3.69
35,291
45-49
8,185,029
5.01
41,018
50-54
6,742,232
8.12
54,723
55-59
4,970,338
14.05
69,811
60-64
3,578,885
21.80
78,002
65-NRA
301,745
11.77
3,550
Total
69,306,132

348,265
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December 26, 2001