PERSPECTIVES: How Common is "Parking" among Social Security Disability Insurance Beneficiaries? Evidence from the 1999 Change in the Earnings Level of Substantial Gainful Activity

by Jody Schimmel, David C. Stapleton, and Jae Song
Social Security Bulletin, Vol. 71, No. 4, 2011

Appendix

Table A-1. DD estimates for the impact of the 1999 SGA earnings-level increase on average monthly from the TWP completion year to the second post-TWP year for the 1996 and 1998 completer cohorts: Full regression results corresponding to Table 4
Characteristic Nominal TWP-year earnings category ($)
0–199 200–499 500–699 700–999 1,000 or more
Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error
DD estimate -0.0054 0.0036 -0.0048 0.0036 0.0220 0.0025 -0.0022 0.0024 -0.0096 0.0035
Indicator for 1998 TWP completer cohort 0.1928 0.0027 -0.1422 0.0027 -0.0457 0.0019 -0.0378 0.0017 0.0330 0.0026
Indicator for second post-TWP year -0.0146 0.0022 -0.0250 0.0028 -0.0015 0.0019 0.0051 0.0018 0.0360 0.0024
Age (years, as of December 31) 0.0021 0.0001 0.0007 0.0001 -0.0005 0.0001 -0.0012 0.0001 -0.0011 0.0001
Male 0.0082 0.0018 -0.0426 0.0019 -0.0081 0.0013 -0.0043 0.0012 0.0468 0.0018
Black -0.0236 0.0052 -0.0012 0.0051 0.0249 0.0035 0.0230 0.0034 -0.0232 0.0051
Hispanic 0.0876 0.0068 -0.0539 0.0062 -0.0014 0.0044 0.0001 0.0042 -0.0323 0.0063
Other race -0.0119 0.0113 -0.0312 0.0105 0.0012 0.0075 -0.0004 0.0071 0.0424 0.0115
White -0.0297 0.0049 0.0235 0.0048 0.0077 0.0033 -0.0009 0.0031 -0.0006 0.0048
Education (years)
0–8 0.0489 0.0051 -0.0204 0.0049 0.0028 0.0035 0.0085 0.0032 -0.0397 0.0043
9–11 0.0245 0.0033 -0.0259 0.0033 0.0045 0.0024 0.0172 0.0023 -0.0203 0.0031
12 -0.0041 0.0021 -0.0098 0.0022 0.0013 0.0015 0.0064 0.0014 0.0063 0.0021
13–15 -0.0241 0.0033 -0.0379 0.0033 -0.0022 0.0024 0.0020 0.0022 0.0623 0.0036
16 or more -0.0434 0.0038 -0.0767 0.0037 -0.0154 0.0026 -0.0055 0.0025 0.1409 0.0044
Primary disabling condition
Major affective disorders 0.0872 0.0165 -0.0023 0.0178 -0.0292 0.0137 -0.0115 0.0124 -0.0442 0.0187
Schizophrenia and psychoses 0.1130 0.0167 0.1045 0.0180 -0.0202 0.0138 -0.0250 0.0125 -0.1724 0.0187
Anxiety and neurotic disorders 0.0806 0.0171 -0.0010 0.0184 -0.0225 0.0141 0.0014 0.0128 -0.0584 0.0192
Other mental disorders 0.0556 0.0169 0.0675 0.0183 -0.0136 0.0140 -0.0097 0.0126 -0.0999 0.0190
Mental retardation 0.0448 0.0165 0.2143 0.0179 -0.0007 0.0138 -0.0307 0.0124 -0.2278 0.0186
Back disorders 0.0797 0.0168 -0.0560 0.0180 -0.0400 0.0139 -0.0122 0.0125 0.0285 0.0190
Musculoskeletal system 0.0663 0.0169 -0.0099 0.0182 -0.0314 0.0139 -0.0188 0.0126 -0.0062 0.0191
Infectious and parasitic diseases 0.0637 0.0225 0.0415 0.0239 -0.0150 0.0176 -0.0240 0.0154 -0.0663 0.0239
HIV/AIDS 0.0323 0.0173 -0.0208 0.0185 -0.0282 0.0143 -0.0133 0.0129 0.0300 0.0197
Neoplasms -0.0343 0.0171 -0.1423 0.0182 -0.0646 0.0140 -0.0217 0.0128 0.2628 0.0197
Endocrine/nutritional 0.0845 0.0173 -0.0156 0.0185 -0.0331 0.0142 -0.0041 0.0129 -0.0317 0.0194
Blood/blood-forming diseases 0.0313 0.0212 -0.0486 0.0222 -0.0473 0.0167 -0.0184 0.0158 0.0830 0.0246
Severe visual impairment 0.0438 0.0181 -0.0523 0.0191 -0.0093 0.0149 0.0593 0.0140 -0.0414 0.0202
Severe hearing impairment 0.0356 0.0175 -0.0006 0.0189 -0.0052 0.0146 0.0043 0.0132 -0.0341 0.0197
Severe speech impairment 0.0569 0.0350 -0.0294 0.0344 -0.0496 0.0236 -0.0187 0.0232 0.0408 0.0386
Nervous system 0.0618 0.0169 0.0450 0.0182 -0.0199 0.0140 -0.0189 0.0126 -0.0679 0.0190
Circulatory system 0.0582 0.0171 -0.0106 0.0184 -0.0210 0.0141 -0.0137 0.0127 -0.0130 0.0193
Respiratory system 0.0591 0.0190 0.0114 0.0203 -0.0174 0.0153 -0.0132 0.0138 -0.0399 0.0209
Digestive system 0.0265 0.0186 -0.0796 0.0194 -0.0593 0.0146 -0.0078 0.0137 0.1201 0.0213
Genitourinary system 0.0259 0.0174 -0.0426 0.0186 -0.0343 0.0143 -0.0196 0.0130 0.0706 0.0199
Skin/subcutaneous tissue 0.1233 0.0288 -0.0435 0.0275 -0.0264 0.0210 -0.0204 0.0189 -0.0330 0.0293
Congenital anomalies 0.0396 0.0228 0.1865 0.0259 0.0010 0.0190 -0.0476 0.0154 -0.1796 0.0229
Injuries 0.0361 0.0168 -0.0561 0.0181 -0.0391 0.0139 -0.0209 0.0126 0.0800 0.0191
Other 0.0505 0.0164 0.0106 0.0177 -0.0186 0.0137 -0.0013 0.0123 -0.0412 0.0186
TWP completion month
January 0.0256 0.0046 -0.0571 0.0045 -0.0100 0.0032 -0.0137 0.0030 0.0553 0.0045
February 0.0110 0.0045 -0.0479 0.0045 -0.0142 0.0032 -0.0130 0.0030 0.0640 0.0044
March 0.0028 0.0044 -0.0467 0.0045 -0.0060 0.0032 -0.0089 0.0030 0.0589 0.0044
April -0.0073 0.0044 -0.0462 0.0044 -0.0051 0.0032 -0.0091 0.0030 0.0678 0.0044
May -0.0146 0.0042 -0.0361 0.0043 -0.0064 0.0031 -0.0075 0.0029 0.0645 0.0042
June -0.0188 0.0043 -0.0377 0.0044 -0.0026 0.0031 0.0001 0.0030 0.0589 0.0043
July -0.0157 0.0044 -0.0362 0.0046 -0.0008 0.0033 -0.0020 0.0031 0.0548 0.0044
August -0.0185 0.0044 -0.0231 0.0046 0.0007 0.0033 0.0015 0.0031 0.0394 0.0044
September 0.0457 0.0039 0.0142 0.0040 -0.0147 0.0027 -0.0167 0.0026 -0.0285 0.0036
October -0.0053 0.0044 -0.0061 0.0046 -0.0010 0.0032 -0.0033 0.0030 0.0156 0.0042
November -0.0050 0.0043 -0.0073 0.0045 0.0002 0.0032 -0.0057 0.0030 0.0177 0.0042
Intercept 0.0501 0.0177 0.3611 0.0190 0.1656 0.0145 0.1663 0.0132 0.2570 0.0197
Number of observations 233,930 121,492 28,678 25,632 58,128
Adjusted R-squared 0.0593 0.0656 0.0071 0.0098 0.0655
SOURCE: SSA's 2007 TRF data merged with MEF data.
NOTE: Omitted categories from the regression model include missing race, missing primary disabling condition, missing education status, and TWP completion month in December.
Table A-2. DD estimates for the impact of the 1999 SGA earnings-level increase on mean monthly earnings from the TWP completion year to the second post-TWP year, by earnings interval in the TWP completion year, for the 1996 and 1998 TWP completer cohorts: Full regression results corresponding to Table 5
Characteristic Nominal TWP-year earnings category ($)
Overall Less than 500 500–699 700–999 1,000 or more
Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error
DD estimate 3.8866 11.6592 15.9866 5.3707 17.2542 11.7817 18.4906 17.2946 -7.6915 39.7519
Indicator for 1998 TWP completer cohort 62.5372 6.2975 5.1518 1.3149 5.1965 1.5006 9.2910 2.2142 -10.1234 18.9262
Indicator for second post-TWP year 44.0383 9.3631 98.6104 4.1510 29.2846 8.4781 36.2898 12.5746 -73.2292 34.4259
Age (years, as of December 31) 1.6058 0.2734 -2.4292 0.1284 -4.0616 0.3218 -3.9092 0.4539 17.5550 0.8874
Male 172.5406 5.7616 0.1783 2.7412 13.6061 6.1874 13.7430 9.2567 348.3814 18.0406
Black -129.0092 31.9313 32.1964 7.1384 -20.4002 16.6308 -34.0154 25.7186 -416.3763 114.2753
Hispanic -205.8652 33.4989 -69.5298 8.3585 -9.5389 20.6536 -8.6954 31.5295 -374.2935 117.6089
Other race 80.5293 46.4551 -12.9934 14.9064 -46.5146 31.7408 43.0093 55.7919 2.3408 140.6085
White -43.3134 32.5433 25.7355 6.8306 -16.5007 16.0853 -2.3386 25.2879 -194.5046 116.6975
Education (years)
0–8 -133.6716 11.8063 -33.4089 4.8667 -12.8438 14.2579 -78.4738 18.2650 -265.6697 48.9207
9–11 -89.2504 7.4623 -10.9616 4.0758 -33.1984 9.1836 -46.3559 12.9199 -261.8110 25.2157
12 5.5262 7.0415 -0.8182 3.1169 3.3928 7.1784 -22.5658 10.6072 -43.6796 23.2824
13–15 150.0496 10.3071 27.6498 5.6339 44.1180 12.3871 26.5202 16.0836 135.0863 25.6982
16 or more 572.3826 20.8756 71.0925 11.0502 67.5711 17.7457 61.6534 22.6099 746.2536 44.2387
Primary disabling condition
Major affective disorders -40.9460 38.2088 9.1347 20.2610 -89.1764 56.0137 -57.0047 66.0713 101.0549 84.9935
Schizophrenia and psychoses -354.2219 37.8175 -30.3048 19.4290 -170.9595 55.7803 -129.8439 64.9280 -257.0454 86.7720
Anxiety and neurotic disorders -83.8368 40.3023 -0.3623 20.3839 -80.3719 57.7183 -28.6832 66.5758 54.0168 96.9753
Other mental disorders -161.8322 38.6253 -3.6513 19.7593 -147.3341 56.1442 -82.0815 65.8156 -0.7567 88.2418
Mental retardation -387.2097 37.4753 -12.5732 19.2890 -153.8104 55.3318 -137.4609 64.1344 -308.4275 85.8993
Back disorders 128.4055 43.0494 -2.3513 20.2472 -98.7899 56.8886 -10.7327 69.2368 211.2670 99.8006
Musculoskeletal system 34.6109 39.6684 13.7045 21.2740 -80.9971 59.7504 -30.5887 67.4419 135.7998 88.1016
Infectious and parasitic diseases -105.0050 53.8016 -2.9983 25.5381 -82.9596 75.8870 -112.5069 98.3791 53.5063 134.5186
HIV/AIDS 184.5564 44.8256 43.7924 23.5558 -74.7737 59.6220 -20.4006 70.1392 309.5777 99.8930
Neoplasms 958.6451 53.3380 57.4691 26.2065 50.9550 63.1949 107.0015 72.9602 889.1284 100.9001
Endocrine/nutritional -42.9501 40.1781 -3.5354 20.6404 -97.9509 57.7633 -39.0733 67.2694 61.0255 92.1967
Blood/blood-forming diseases 463.7903 75.1694 22.5105 34.5133 -99.8819 73.1534 -9.7780 89.1374 799.5738 162.5179
Severe visual impairment -68.4195 41.5947 -9.4573 21.7428 -40.1478 58.9789 -24.9684 66.9748 55.4097 97.2393
Severe hearing impairment -57.9384 39.8701 48.9564 22.0228 -74.1816 61.5778 -5.1546 68.7856 -91.4302 89.2821
Severe speech impairment 54.3205 87.9516 8.9965 44.4032 -156.6640 81.5279 93.7077 34.4024 20.1016 194.9995
Nervous system -47.8123 45.4254 4.8625 19.9173 -133.9343 56.6584 -38.2057 66.3530 306.8841 129.7971
Circulatory system 47.7596 40.9301 -1.6673 20.2633 -93.4275 57.7040 -49.9544 68.3519 160.0718 92.0725
Respiratory system -8.2694 50.8713 13.1909 23.7228 -98.2870 61.8202 -44.7192 73.7429 195.9551 141.6386
Digestive system 451.0666 54.3847 24.3395 29.4452 5.7970 72.6930 -48.5661 75.3266 546.2329 109.8123
Genitourinary system 252.1342 43.2640 14.4115 21.6954 -58.7977 59.6275 -0.4348 69.1857 407.8473 93.8453
Skin/subcutaneous tissue -57.6844 62.9407 -25.2792 33.5316 -137.9435 100.5433 59.7690 49.9449 40.2684 151.6898
Congenital anomalies -303.0858 46.6541 -8.0281 23.7773 -145.7737 66.1756 -125.0023 8.9854 -0.1141 156.5348
Injuries 250.9805 39.9722 19.6082 20.7594 -62.7332 57.7010 71.1137 68.7173 330.5153 86.4934
Other -59.2039 37.6178 20.0622 19.3356 -63.0866 55.4150 -24.0432 63.9009 17.5271 83.1404
TWP completion month
January 102.9451 17.1940 -64.5378 5.9937 -59.8878 14.5034 -98.6031 20.6147 27.2923 76.8734
February 127.7342 20.1746 -59.9759 5.8593 -62.4709 16.6615 -86.7749 21.8496 18.3566 84.2944
March 108.2659 16.5926 -54.3847 6.0666 -65.3751 14.3197 -115.0781 18.4321 -17.0366 73.9765
April 131.5672 16.7258 -49.7944 5.7252 -71.2574 14.1684 -88.9445 20.6604 -35.6380 74.7174
May 147.0056 16.4089 -39.6249 5.8072 -38.0231 14.1417 -107.7016 19.1058 6.1093 73.9084
June 121.1597 16.4305 -41.1944 6.0936 -64.5903 14.1988 -70.3646 24.8940 -64.7611 74.6442
July 118.1110 16.7243 -28.1850 6.3087 -75.8079 13.4365 -97.3134 18.9568 -32.7231 75.5382
August 81.5598 16.5385 -19.6110 6.4428 -45.9465 14.7548 -63.2083 19.4302 -62.0353 76.1947
September -82.5369 15.6628 -53.0679 6.1563 -45.2542 12.9009 -64.5756 19.8421 -48.1222 77.0632
October 29.0923 16.5122 -22.0641 6.7304 -12.0151 16.2251 -62.5163 20.9795 -102.1910 77.2100
November 16.1391 16.0215 -13.3835 5.8052 -13.3883 14.1021 -34.7147 19.6629 -90.1469 76.3673
Intercept 634.2349 52.9953 355.2670 21.4314 890.0394 58.3915 1,109.1490 70.1256 1,244.3165 176.6289
Number of observations 233,930 121,492 28,678 25,632 58,128
Adjusted R-squared 0.0504 0.0217 0.0151 0.0109 0.0391
SOURCE: SSA's 2007 TRF data merged with MEF data.
NOTE: Omitted categories from the regression model include missing race, missing primary disabling condition, missing education status, and TWP completion month in December.
Table A-3. DD estimates for the impact of the 1999 SGA earnings-level increase on the number of NSTW months from the TWP completion year to the second post-TWP year, by earnings interval in the TWP completion year, for the 1996 and 1998 TWP completer cohorts: Full regression results corresponding to Table 6
Characteristic Nominal TWP-year earnings category ($)
Overall Less than 500 500–699 700–999 1,000 or more
Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error Parameter estimate Standard error
DD estimate -0.1314 0.0317 -0.2946 0.0312 -0.6312 0.0858 -0.2244 0.1028 0.0265 0.0704
Indicator for 1998 TWP completer cohort 0.0973 0.0118 0.0448 0.0090 -0.0598 0.0304 -0.0252 0.0372 0.0330 0.0251
Indicator for second post-TWP year 2.6208 0.0235 1.5796 0.0234 2.7910 0.0653 3.5870 0.0772 4.5341 0.0544
Age (years, as of December 31) -0.0228 0.0008 -0.0186 0.0008 -0.0353 0.0022 -0.0262 0.0028 -0.0144 0.0020
Male 0.2840 0.0163 0.2172 0.0158 -0.0479 0.0438 -0.2274 0.0536 0.0410 0.0370
Black -0.0701 0.0457 -0.0190 0.0472 0.0704 0.1291 -0.1092 0.1490 -0.2063 0.0980
Hispanic 0.1272 0.0583 0.4507 0.0640 0.1441 0.1642 -0.1698 0.1859 -0.0678 0.1264
Other race 0.3734 0.1044 0.1740 0.1135 -0.0626 0.2954 0.1883 0.3322 0.3438 0.1955
White -0.1433 0.0433 -0.2144 0.0445 -0.1658 0.1246 -0.0980 0.1433 -0.0268 0.0905
Education
0–8 -0.0816 0.0409 0.0800 0.0398 0.1652 0.1116 -0.2089 0.1390 -0.1620 0.1097
9–11 -0.0323 0.0281 0.1126 0.0288 -0.1226 0.0712 -0.0340 0.0876 -0.3163 0.0685
12 0.0667 0.0192 0.0469 0.0188 -0.0169 0.0514 -0.0041 0.0612 -0.0350 0.0424
13–15 0.3908 0.0316 0.1986 0.0335 0.1727 0.0844 0.1558 0.0983 0.1212 0.0598
16 or more 0.7806 0.0384 0.3994 0.0442 0.3773 0.1124 -0.1111 0.1224 0.2256 0.0626
Primary disabling condition
Major affective disorders 0.0208 0.1619 -0.0100 0.1796 -0.0349 0.3946 0.2386 0.4835 0.5437 0.3572
Schizophrenia and psychoses -0.8816 0.1624 -0.4985 0.1794 -0.2658 0.3980 0.1561 0.4889 0.2527 0.3654
Anxiety and neurotic disorders 0.0228 0.1669 0.0088 0.1846 0.1474 0.4094 0.5129 0.4976 0.4435 0.3696
Other mental disorders -0.3965 0.1646 -0.2740 0.1817 -0.4417 0.4015 0.1394 0.4938 0.4684 0.3670
Mental retardation -1.2869 0.1614 -0.6458 0.1788 -0.6342 0.3944 0.0335 0.4876 0.4694 0.3724
Back disorders 0.6413 0.1645 0.4379 0.1835 0.1201 0.4022 0.5837 0.4916 0.8159 0.3600
Musculoskeletal system 0.2678 0.1651 0.1124 0.1828 -0.0324 0.4042 0.3622 0.4958 0.7775 0.3625
Infectious and parasitic diseases -0.0428 0.2101 -0.2066 0.2144 -0.0893 0.5092 -0.2814 0.6670 1.2552 0.4679
HIV/AIDS 0.7021 0.1709 0.3011 0.1928 0.2587 0.4174 0.6846 0.5087 1.2490 0.3665
Neoplasms 2.1910 0.1715 1.2690 0.2084 1.0409 0.4457 1.0694 0.5131 1.7512 0.3608
Endocrine/nutritional 0.2256 0.1681 0.0556 0.1854 0.1694 0.4134 0.4325 0.5021 0.9175 0.3694
Blood/blood-forming diseases 0.8994 0.2161 0.0504 0.2429 0.2083 0.5335 0.8622 0.6451 1.4116 0.4180
Severe visual impairment -0.5939 0.1738 -0.3360 0.1903 -1.1611 0.4142 -1.5715 0.5050 0.2785 0.3914
Severe hearing impairment 0.5063 0.1724 0.2675 0.1913 0.2821 0.4217 0.9691 0.5104 1.3214 0.3762
Severe speech impairment 0.4080 0.3326 0.0326 0.3619 -0.4247 0.7968 0.7777 0.9256 1.4060 0.6162
Nervous system -0.1657 0.1648 -0.2160 0.1814 -0.4424 0.4024 0.6424 0.4968 0.7682 0.3644
Circulatory system 0.2228 0.1666 0.0184 0.1840 -0.0646 0.4068 0.3992 0.5012 0.7571 0.3647
Respiratory system 0.1207 0.1812 -0.0010 0.1955 0.1229 0.4430 0.3743 0.5513 0.6954 0.4006
Digestive system 1.0446 0.1847 0.3876 0.2111 0.5358 0.4930 0.4946 0.5418 1.1272 0.3798
Genitourinary system 1.0117 0.1726 0.4386 0.1954 0.4908 0.4244 0.8377 0.5137 1.4699 0.3674
Skin/subcutaneous tissue 0.2432 0.2585 0.4297 0.2881 -1.2516 0.5683 0.7864 0.8675 0.8251 0.5712
Congenital anomalies -1.0403 0.2046 -0.5957 0.2016 -0.0883 0.5567 -0.5132 0.7535 0.7373 0.5833
Injuries 0.9527 0.1658 0.4606 0.1860 0.1261 0.4068 0.8561 0.4957 1.2820 0.3601
Other 0.2586 0.1609 0.1206 0.1789 0.4380 0.3922 0.6017 0.4805 0.8940 0.3554
TWP completion month
January 1.4062 0.0431 -0.0337 0.0416 0.7770 0.1162 1.7724 0.1412 3.3805 0.0967
February 1.2590 0.0414 -0.0947 0.0404 0.5190 0.1141 1.4563 0.1363 2.9446 0.0928
March 1.0814 0.0404 -0.0744 0.0408 0.4156 0.1079 1.2204 0.1310 2.4209 0.0917
April 0.9308 0.0391 -0.1504 0.0398 0.2126 0.1037 0.7597 0.1258 2.0860 0.0881
May 0.7810 0.0373 -0.1259 0.0385 0.2464 0.1020 0.6184 0.1206 1.6622 0.0857
June 0.6036 0.0373 -0.1682 0.0390 0.1070 0.1000 0.4729 0.1172 1.1782 0.0864
July 0.3755 0.0383 -0.2203 0.0396 -0.1627 0.1004 0.2120 0.1214 0.8284 0.0896
August 0.1721 0.0384 -0.2256 0.0398 -0.1847 0.1033 0.0275 0.1220 0.4442 0.0924
September -0.3132 0.0318 -0.2671 0.0329 -0.4202 0.0913 -0.4679 0.1093 -0.0346 0.0860
October -0.0865 0.0373 -0.2100 0.0386 -0.2496 0.1030 -0.3229 0.1222 -0.0236 0.0942
November -0.0132 0.0370 -0.1147 0.0389 -0.0920 0.1042 -0.1786 0.1214 0.1028 0.0940
Intercept 1.2935 0.1711 1.1024 0.1890 2.3566 0.4207 2.0928 0.5148 1.1272 0.3809
Number of observations 233,930 121,492 28,678 25,632 58,128
Adjusted R-squared 0.146 0.0868 0.1282 0.1794 0.2765
SOURCE: SSA's 2007 TRF data merged with MEF data.
NOTE: Omitted categories from the regression model include missing race, missing primary disabling condition, missing education status, and TWP completion month in December.
Table A-4. AWI-adjusted DD estimates for the impact of the 1999 SGA earnings-level increase on average monthly earnings from the TWP completion year to the second post-TWP year for the 1996 and 1998 completer cohorts
Average monthly earnings ($) Percentage of cohort with earnings in category DD estimate of the effect of the
SGA earnings-level increase
Year of TWP completion Second post-TWP year Point estimate t-statistic 95 percent confidence interval
1996 1998 1996 1998
0–199 15.19 15.47 36.00 35.64 -0.63 -1.79 -0.75 0.06
200–499 30.87 31.98 20.96 20.27 -1.81 -5.00 0.35 -1.10
500–699 14.71 13.14 8.82 9.30 2.05 7.75 -3.00 2.57
700–999 11.66 11.24 6.95 7.06 0.52 2.15 -1.44 1.00
1,000 or more 27.57 28.16 27.27 27.74 -0.12 -0.32 -1.33 0.62
SOURCE: SSA's 2007 TRF data merged with MEF data.
NOTES: DD estimates are regression-adjusted to control for differences in the 1996 and 1998 cohorts. Earnings adjusted for wage growth to year-2000 dollars using the contemporaneous AWI.
Table A-5. AWI-adjusted DD estimates for the impact of the 1999 SGA earnings-level increase on mean monthly earnings from the TWP completion year to the second post-TWP year, by earnings interval in the TWP completion year, for the 1996 and 1998 TWP completer cohorts
Average monthly earnings in the TWP year ($) Percentage of cohort in category Change in mean monthly earnings of cohort ($) DD estimate of the impact of the
SGA earnings-level increase
1996 1998 1996 1998 Estimate t-statistic 95 percent confidence interval Percentage estimate
Total 100.0 100.0 -47.28 -46.12 1.17 0.10 -21.82 24.16 0.1
Weighted total 100.0 100.0 -47.29 -46.12 1.11 0.11 -18.72 20.94 0.1
Less than 500 46.06 47.45 88.23 86.14 -2.08 -0.36 -13.43 9.27 -0.6
500–699 14.71 13.14 -19.33 -11.93 7.39 0.73 -12.50 27.28 1.3
700–999 11.66 11.24 -51.54 -36.02 15.52 0.97 -15.92 46.96 2.0
1,000 or more 27.57 28.16 -286.80 -288.97 -2.17 -0.06 -73.24 68.90 -0.1
SOURCE: SSA's 2007 TRF data merged with MEF data.
NOTES: The change in monthly earnings is calculated from the TWP completion year to 2 years later. DD estimates are regression-adjusted to control for differences in the 1996 and 1998 cohorts. Within each group, the percentage estimate is the DD estimate divided by the mean earnings in the second post-TWP year (2000) of the 1998 TWP completers, net of the DD estimate for the group. Earnings adjusted for wage growth to year-2000 dollars using the contemporaneous AWI.
Table A-6. AWI-adjusted DD estimates for the impact of the 1999 SGA earnings-level increase on the number of NSTW months from the TWP completion year to the second post-TWP year, by earnings interval in the TWP completion year, for the 1996 and 1998 TWP completer cohorts
Average monthly earnings in the TWP year ($) Percentage of cohort in category Change in the mean number of NSTW months of cohort DD estimate of the impact of the
SGA earnings-level increase
1996 1998 1996 1998 Estimate t-statistic 95 percent confidence interval Percentage estimate
Total 100.0 100.0 2.62 2.49 -0.13 -4.14 -0.19 -0.07 -3.5
Weighted total 100.0 100.0 2.62 2.49 -0.13 -8.42 -0.16 -0.10 -3.4
Less than 500 46.06 47.45 1.49 1.27 -0.22 -6.79 -0.28 -0.16 -12.8
500–699 14.71 13.14 2.39 1.99 -0.41 -5.53 -0.56 -0.26 -13.1
700–999 11.66 11.24 3.15 3.20 0.05 0.46 -0.16 0.26 1.0
1,000 or more 27.57 28.16 4.41 4.50 0.09 1.39 -0.04 0.22 1.3
SOURCE: SSA's 2007 TRF data merged with MEF data.
NOTES: The change in the NSTW months is calculated from the TWP completion year to 2 years later. DD estimates are regression-adjusted to control for differences in the 1996 and 1998 cohorts. Within each group, the percentage estimate is the DD estimate divided by the mean number of NSTW months in the second post-TWP year (2000) of the 1998 TWP completers, net of the DD estimate for the group. Earnings adjusted for wage growth to year-2000 dollars using the contemporaneous AWI.