Research and Analysis by John C. Hennessey
Markov models have been widely used for the analysis and prediction of shifts in population distribution over time. The point of departure for most of these analyses has been the finite state, time stationary Markov chain. The usual Markov chain model has, however, been shown to be inadequate for most social science applications.
This paper presents a particular kind of discrete time nonstationary Markov chain. Such chains will be built using a mathematical quantity called a causative matrix.
Comparison of Individual Characteristics and Death Rates of Disabled-Worker Beneficiaries Entitled in 1972 and 1985
A Comparison of the Recovery Termination Rates of Disabled-Worker Beneficiaries Entitled in 1972 and 1985
The Effect of Vocational Rehabilitation and Work Incentives on Helping the Disabled-Worker Beneficiary Back to Work
This article is the second in a series of articles that use data from the New Beneficiary Followup survey to analyze the work effects of the Social Security Administration's Disability Insurance beneficiaries. Survival analysis techniques are used to determine the effect of vocational rehabilitation efforts and work incentive program provisions on actual work outcomes. The findings indicate that the demographic variables of age, gender, race, education, and marital status affect the tendency to return to work in the expected way. The results suggest a possible disincentive effect may be built into certain work incentive provisions of the program. The encouraging news is that the vocational rehabilitation efforts seem to have a positive effect on the tendency to return to work. Physical therapy, vocational training, general education, and job placement efforts all seem to increase the tendency to go back to work.
Congress is currently placing considerable emphasis on returning disabled-worker beneficiaries to work. However, going back to work is only the first step in the complex process of program termination due to work and trust fund savings. Not only must the beneficiary get a job, but also the work effort must be sustained at what is considered a substantial gainful activity (SGA) level by the disability program (so that an SGA termination will result) and a reasonable living condition must be achieved by the beneficiary(so that the person is motivated to continue working and lose benefits). This articles focuses on those factors that affect the ability of the beneficiary to sustain such a work effort. Combined with previous findings about returning to work, we begin to see the overall effect of the factors on work efforts.
Beneficiaries who have physical therapy rehabilitation have a higher tendency to start working and a lower tendency to stop. Those with vocational training or general education have a higher tendency to start working, but these factors do not help to sustain the effort. Beneficiaries who were helped with job placement have a higher tendency to start work, but they also have a higher tendency to stop. If beneficiaries knew about the trial-work period, but not about either the extended period of eligibility or Medicare continuation, then they had a higher tendency to start work and a higher tendency to stop. However, if they knew about all three work-incentive provisions, then the tendency to work was not affected.
How Post Secondary Education Improves Adult Outcomes for Supplemental Security Income Children with Severe Hearing Impairments
This article uses a unique longitudinal dataset based on administrative data from the National Technical Institute for the Deaf (NTID) linked to Social Security Administration (SSA) microdata to conduct a case study of Supplemental Security Income (SSI) children who applied for postsecondary education at NTID. The authors estimate the likelihood that SSI children who apply to NTID will eventually graduate relative to other hearing impaired applicants, as well as the influence of graduation from NTID on participation in the SSI program as adults and later success in the labor market. Findings indicate that SSI children are substantially less likely to graduate from NTID than their fellow deaf students who did not participate in the SSI program as children, but that those who do graduate spend less time in the SSI adult program and have higher age-earnings profiles than those who do not graduate.
This article presents basic findings about the job patterns of disabled-worker beneficiaries covered under the Social Security Administration's Disability Insurance (DI) program as reported in the New Beneficiary Follow-up survey. Beneficiaries are asked retrospective questions about labor-force participation from the time of their first entitlement to disability benefits to the time of the interview.
Twelve percent of those persons who enter the DI program as nonworking beneficiaries start a job during their entitlement to benefits. The mean time to the start of the job was 3.4 years. Of those who start a job, 50 percent end the job before the end of their entitlement. Most of these persons leave the job for health-related reasons and, for most of them, the employer does not play a major role in their decision to stop working. For those who end the first job and are employed in subsequent jobs, the percentage who recover while still in the job decreases as the number of jobs increases.
Statistical Methodology for a Comparison of the Individual Characteristics and Death Rates of Disabled-Worker Beneficiaries Entitled in 1972 and 1985
This paper contains the technical details about the statistical methodology used in the article, "A Comparison of the Individual Characteristics and Death Rates of Disabled-Worker Beneficiaries Entitled in 1972 and 1985," published in the Fall 1992 issue of the Social Security Bulletin, vol. 55, no. 3. Logistic regression techniques were used to test for differences between the covariate distribution of the 1972 and the 1985 entitlement cohorts. Survival analysis techniques were used to model the death rates of the two cohorts.
Testing the Predictive Power of a Proportional Hazards Semi-Markov Model of Postentitlement Histories of Disabled Male Beneficiaries
In the Disability Amendments of 1980 (P.L. 96-265), Congress mandated that certain experiments be carried out which are designed to encourage disabled beneficiaries to return to work and save trust fund monies. A research plan has been developed which would offer alternative program provisions, experimentally, to different samples of beneficiaries. An observation period of three to four years will be possible before a report to Congress must be written. However, a period of this length is not sufficient to observe, fully, the postentitlement experience of disabled beneficiaries. In order to estimate the long run effects of the experiments, a method is needed which can project postentitlement behavior beyond the observation period.
This paper tests the ability of proportional hazards semi-Markov model to make accurate predictions in this type of setting. The data are divided into two segments: the first 14 calendar quarters and the last 16 quarters. Various types of rate functions including proportional hazards rate functions are estimated on the first segment, then projected over the entire 30 quarters and compared to the actual data. The proportional hazards rate functions are then used in a simulation to estimate monthly benefit cost to the social security disability trust fund over the last 16 quarters, using an age-dependent, absorbing, semi-Markov model. The model does a very good job of capturing the dynamics of the process and should prove quite useful as one of the major components in an analysis of the Work Incentive Experiments.