Selected Research & Analysis: Modeling (Simulations, Projections)
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Using a lifecycle model, the authors examine the implications of persistent low real interest rates and low wage growth for individuals nearing retirement. Low returns and low wage growth are found to affect welfare substantially, often producing large compensating variations. Low economywide wage growth has a much larger welfare effect than low individual wage growth, largely because the Social Security benefit formula is progressive and incorporates wage indexing. Low economywide wage growth undercuts the effects of wage indexation as average wages fall along with individual wages. Low returns raise the optimal Social Security claiming age and the marginal benefit of working longer, while low wage growth decreases the marginal benefit of working longer. Low returns also increase the relative price of consumption during retirement, suggesting that individuals may wish to reduce future consumption relative to current consumption. The authors then compare these findings with standard financial planning advice.
A stylized example neatly and efficiently answers the question of how much Social Security benefits would change because a stylized worker's situation is straightforward and does not require demographic or statistical knowledge to understand. However, it leaves other questions unanswered, such as how many people are like that worker and would anyone fall into poverty? To answer these types of questions, you need to use distributional analysis, which examines how something, such as income, benefits, or policy effects, is distributed across a group of people. This note describes the use of distributional analysis in Social Security policy discussions by analyzing the distributional effects of three real-life Social Security policy options.
This article explores the causes of growth in the number of disabled workers on the Social Security Disability Insurance (DI) rolls from 1980 through 2010 by estimating the probability of a DI beneficiary's program exit because of recovery, death, or conversion to retired-worker beneficiary. The author uses Social Security administrative data and a competing-risks model to estimate DI exit probabilities by cause and beneficiary sex, age, and disability type. Cumulative exit probabilities are calculated for beneficiaries over their first 9 years on the DI rolls. The author also examines possible changes over time by comparing outcomes for the 1980s with those for the 1990s.
Choosing the claiming age that maximizes the expected present value of lifetime Social Security retirement benefits requires a survival function to account for an individual's prospective longevity along with the specification of a rate by which to discount the future benefit payments for each claiming age. This article evaluates optimal claiming ages for prospective beneficiaries across a range of 81 real discount rate options (specified in increments of one-tenth of 1 percent) from 0 percent to 8 percent, considering the survival functions for men and women born in 1952. It examines the implications of choosing a given rate as well as the sensitivity of the optimal claiming age to a specific rate choice.
The rising cost of employer contributions for employee health insurance reduces the percentage of compensation subject to Social Security payroll taxes. This article uses the Medical Expenditure Panel Survey to analyze trends in the cost of employer health insurance contributions relative to money wages and total compensation. The analysis shows how increasing employer health insurance premium costs from 1996 to 2008 reduced the percentage of compensation subject to payroll taxes, and it predicts the effects of health insurance reform on taxable compensation.
The Growth in Social Security Benefits Among the Retirement-Age Population from Increases in the Cap on Covered Earnings
This article investigates how raising the maximum level of earnings subject to the Social Security payroll tax leads to the "leakage" of portions of the additional revenue into higher benefit payments. Using data from the Health and Retirement Study, the authors simulate the effects of changes in maximum taxable earnings for cohorts approaching retirement age over a 24-year period. They find, roughly, that almost half of the additional tax revenue from having raised the maximum earnings subject to the payroll tax has leaked into higher benefits.
The Sensitivity of Proposed Social Security Benefit Formula Changes to Lifetime Earnings Definitions
Several Social Security proposals have included benefit formula changes that apply to earners above a specified percentage of the combined male and female (unisex) lifetime earnings distribution. This study finds that if Social Security's median unisex average indexed monthly earnings (AIME) amount is used to define an earnings threshold below which benefits will be held unreduced, the percentage of fully insured men subject to benefit reductions (70 percent) will exceed the unisex estimate of the population subject to benefit reductions (50 percent) by 20 percentage points. If policymakers wish to adjust future benefits and focus benefit reductions on middle or high primary or full-time wage earners in a household, the male, rather than unisex, AIME would come closer to achieving such a goal.
Assessing the Performance of Life-Cycle Portfolio Allocation Strategies for Retirement Saving: A Simulation Study
The investment performance of life-cycle portfolio allocation strategies is evaluated using a stochastic simulation based on historical asset returns during 1926–2008. Lifetime contribution streams to the accounts are determined using the actual earnings histories of 13,000 workers born in 1915–1942. The results are compared with those of four alternative strategies that vary in terms of investor exposure to stock and bond market risk.
This article discusses the advantages and limitations of using administrative data for research, examines how linking administrative data to survey results can be used to evaluate and improve survey design, and discusses research studies and SSA statistical products and services that are based on administrative data.
This paper evaluates the out-of-sample performance of two stochastic models used to forecast age-specific mortality rates: (1) the model proposed by Lee and Carter (1992); and (2) a set of univariate autoregressions linked together by a common residual covariance matrix (Denton, Feavor, and Spencer 2005).
As the first in a trio of articles devoted to incorporating immigration into policy models, this article traces the history of research on immigrant earnings. It focuses on how earnings trajectories of immigrants differ from those of U.S. natives, vary across immigrant groups, and have changed over time. The highlighted findings underscore key lessons for modeling immigrant earnings and pave the way for representing the earnings trajectories of immigrants in policy models.
Complementing the second paper's focus on forecasting immigrant earnings and emigration in a "closed system" for a given population, the last article of the trilogy explores how to project immigrant earnings for an "open system"—a system that includes future immigrants. A simple method to project future immigrants and their earnings is presented.
Given immigration's recent resurgence as an important demographic fact in the U.S. economy, U.S. policy modelers are just beginning to grapple with how best to integrate immigrants into policy models. Building on the research reviewed in the first article of this series, this article puts forth a conceptual basis for incorporating immigration into a key type of policy model—microsimulation—with a focus on the projection of immigrant earnings.
This article presents the distributional effects of changing the Social Security indexing scheme, with an emphasis on the effects upon disabled-worker beneficiaries. Although a class of reform proposals that would slow the rate of growth of initial benefit levels over time—including price indexing and longevity indexing—initially appear to affect all beneficiaries proportionally, there can be different impacts on different groups of beneficiaries. The impacts between and within groups are mitigated by (1) the offsetting effect of changes in Supplemental Security Income benefits at the lower tail of the income distribution, and (2) the dampening effect of other family income at the upper tail of the income distribution. The authors present estimates of the size of these effects.
Old-Age, Survivors, and Disability Insurance (OASDI, Social Security) benefits are indexed for inflation to protect beneficiaries from the loss of purchasing power implied by inflation. In the absence of such indexing, the purchasing power of Social Security benefits would be eroded as rising prices raised the cost of living. Recently, the Consumer Price Index used to calculate the Cost-of-Living-Adjustment (COLA) for OASDI benefits has come under increased scrutiny. Some argue that the current index does not accurately reflect the inflation experienced by seniors and that COLAs should be larger. Others argue that the measure of inflation underlying the COLA has technical limitations that cause it to overestimate changes in the cost of living and that COLAs should be smaller. This article discusses some of the issues involved with indexing Social Security benefits for inflation and examines the ramifications of potential changes to COLA calculations.
The Board of Trustees of the Federal Old-Age and Survivors Insurance and Disability Insurance (OASDI) Trust Funds reports on the current and projected future financial status of the trust funds annually. The Trustees project trust fund finances 75 years into the future. Mortality is one key demographic assumption that feeds into these long-range projections. This article reviews a range of predictions about long-term mortality improvement and assesses where the Trustees' 75-year mortality projection falls within this range. In general, the predictions of future mortality declines in the 2004 Social Security Trustees Report tend to be in the mainstream of professional actuarial and international official government opinion and to be lower than the majority of the small group of demographers who produce comparable estimates.
This article estimates effects of future growth in income on the poverty rates of the elderly. If real earnings and other income were to increase steadily at 1 percent per year, poverty among the elderly, 10.5 percent in 1997, would decrease to about 7.2 percent in 2020 and to 4.1 percent in 2047, assuming no Social Security benefit reductions to maintain solvency. The article discusses several other aspects that might affect future poverty rates, including changes in other income components like Supplemental Security Income, earnings, and pensions; changes in longevity and marital patterns; and changes in the distribution of earnings.
This article presents the Supplemental Security Income (SSI) Financial Eligibility Model developed in the Division of Policy Evaluation of the Office of Research, Evaluation, and Statistics. Focusing on the elderly, the article simulates five potential changes to the SSI eligibility criteria and presents the effects of those simulations on SSI participation, federal benefits, and poverty among the elderly. Finally, the article discusses future directions for research and potential improvements to the model.
This paper asks whether information about immigrants other than their age, education, and years since migration can be productively used to project their earnings. Although many factors could affect immigrants' earnings, what is most useful for Social Security modeling purposes is relevant information that is readily available on a continuous basis. Country of origin is a good candidate as it is regularly and readily available from several administrative and survey data sources.
In this paper, microdata samples from the 1960–1990 censuses are used to examine the relationship between country of origin and the earnings of immigrants. By following cohorts of immigrants over 10-year intervals, we learn how country of origin affects the initial earnings of immigrants and how the relationship between country of origin and immigrants' earnings changes as immigrants live in the United States. The paper also presents theoretical insights and empirical evidence about the underlying causes of the link between country of origin and immigrants' earnings.
This article asks whether information about immigrants beyond their age, education, and years since migration can be productively used to project their earnings. Although many factors could affect immigrant earnings, what is most useful for Social Security modelling purposes is relevant information that is readily available on a continuous basis. Country of origin is a good candidate, as it is regularly and readily available from several administrative and survey data sources.
In this article, microdata samples from the 1960-90 censuses are used to examine the relationship between country of origin and the earnings of immigrants. By following cohorts of immigrants over 10-year intervals, we learn how country of origin affects the initial earnings of immigrants and how the relationship between country of origin and immigrant earnings changes as immigrants continue to live in the United States. The article also presents theoretical insights and empirical evidence about the underlying causes of the link between country of origin and immigrant earnings.
Each year the Social Security Administration forecasts the financial status of the Old-Age, Survivors, and Disability Insurance (OASDI) programs by projecting trends in key variables such as the labor force participation and earnings of the U.S. population. In the difficult task of projecting the long-term financial status of Social Security, assumptions are made concerning the relationship of immigrants to Social Security. An important aspect of that relationship is the emigration of immigrants.
This paper describes the general assumptions related to the level and timing of emigration that underlie projections of Social Security's financial status and examines how closely these assumptions fit research findings based on a variety of data sources. Previous trends in emigration and factors that may affect current and future levels of emigration are described. The paper also presents theoretical expectations and empirical evidence concerning the timing of emigration.
This working paper includes two interrelated papers presented at the annual meeting of the American Statistical Association in August 1991. The papers outline the central ideas and the progress to date associated with the development of a new microsimulation model for program analysis at the Social Security Administration (SSA). The first paper, Rationale for a SIPP-Based Microsimulation Model of SSI and OASDI, relates the analytical potential of the proposed model to data development efforts intended to overcome specific information gaps. It also suggests areas in which the model can enrich SSA's ability to address issues specifically related to either the Supplemental Security Income or Old-Age, Survivors, and Disability Insurance programs or issues requiring comparative analysis of both programs. The second paper, Implementing an SSI Model Using the Survey of Income and Program Participation, describes progress on a preliminary version of the model focusing on the SSI program. It includes a brief description of the model, presentation and discussion of initial results, and comparisons with other studies.
A Note on Maximum Likelihood Estimation of Discrete Choice Models from the 1978 Survey of Disability and Work
This paper demonstrates an alternative maximum likelihood procedure for estimating discrete choice models in retrospective samples, such as a model of SSA disability beneficiaries or application status in the 1978 Survey of Disability and Work.
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.
Estimation of Disability Status as a Single Latent Variable in a Model with Multiple Indicators and Multiple Causes
In this paper, we are concerned with the underlying structure of self-definitions of disability. Our purpose is to identify the contribution of exertional and nonexertional impairment and the contributions of such nonmedical factors as age, sex, and education to the individuals' assessment of their own situations. On a statistical level, we seek to accomplish a substantial reduction of a large number of data items into a form that can be used conveniently in subsequent behavioral analyses.
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.