Semiparametric estimation of count regression models

This paper develops a semiparametric estimation approach for mixed count regression models based on series expansion for the unknown density of the unobserved heterogeneity. We use the generalized Laguerre series expansion around a gamma baseline density to model unobserved heterogeneity in a Poisson mixture model. We establish the consistency of the estimator and present a computational strategy to implement the proposed estimation techniques in the standard count model as well as in truncated, censored, and zero-inflated count regression models. Monte Carlo evidence shows that the finite sample behavior of the estimator is quite good. The paper applies the method to a model of individual shopping behavior. © 1999 Elsevier Science S.A. All rights reserved.

Feasibility of using technology to disseminate evidence to rural nurses and improve patient outcomes

Background: Rural African American women receive less frequent mammography screening and die of breast cancer at a higher rate than is seen in the general population. To overcome this disparity, it is necessary to assist rural providers in their efforts to influence women to obtain screening. Method: This study examined the feasibility of using distance education to disseminate knowledge about timely and appropriate mammography screening to rural nurses, using patient outcome data to evaluate the effectiveness of this intervention. Results: Overall, there was a decline in referrals and mammography screening, but the intervention group centers showed a smaller decline after the educational intervention than did the control group. Conclusion: The findings show the effect of dissemination of information and the feasibility of using patient outcome data for educational evaluation. Neighboring academic health centers and nursing schools should include in their mission the provision of educational programs for relatively isolated rural nurses.

Annual miles drive used car prices

This paper investigates whether the net benefits from owning a vehicle, proxied by annual miles driven, explain the price declines observed over a vehicle's life. We first model the household decision on how much to drive each of its vehicles. Then we empirically establish that variation in household annual miles across brands explains observed price declines. Furthermore, the effect of vehicle age on annual miles decisions (and consequently on market value) depends on household characteristics and the composition of the vehicle stock owned.

Are lemons really hot potatoes?

We model the hazard rate for car ownership spells. Our model allows us to distinguish among different types of adverse selection effects by observing the type of unobserved heterogeneity across owners of the same car. Our empirical results strongly suggest that there is a lemons effect because there is significant unobserved heterogeneity. However, they also suggest that the lemons effect is caused by the first owner rather than the manufacturer. Had the manufacturer created the lemon, the unobserved heterogeneity would be positively correlated over all owners of a given car. Instead we observe a negative correlation between the unobserved heterogeneity term for the first owner and the unobserved heterogeneity term for subsequent owners. © 2008 Elsevier B.V. All rights reserved.

Long-term care and family bargaining

We present a structural model of how families decide who should care for elderly parents. We use data from the National Long-Term Care Survey to estimate and test the parameters of the model. Then we use the parameter estimates to simulate the effects of the existing long-term trends in terms of the common but untested explanations for them. Finally, we simulate the effects of alternative family bargaining rules on individual utility to measure the sensitivity of our results to the family decision-making assumptions we make.

Fertility choice, land, and the Malthusian hypothesis

In a standard overlapping generations growth model, with a fixed amount of land and endogenous fertility, the competitive economy converges to a steady state with a zero population growth rate and positive consumption per capita. The Malthusian hypothesis is interpreted as a positive statement about the relationship between population growth and consumption per-capita, when production exhibits diminishing returns to labor and there is a fixed amount of land essential for production. Even when individuals care only about the number of their children and not about their children's welfare, the equilibrium is such that they eventually would choose to have only one child for each adult. Hence, if Malthus's "positive check' on population is the result of the response of optimizing agents to competitively determined prices, Malthus's pessimistic conjecture is not necessarily true, even though his other assumptions hold. -from Authors

Formal home health care, informal care, and family decision making

We use the 1993 wave of the Assets and Health Dynamics Among the Oldest Old (AHEAD) data set to estimate a game-theoretic model of families' decisions concerning the provision of informal and formal care for elderly individuals. The outcome is the Nash equilibrium where each family member jointly determines her consumption, transfers for formal care, and allocation of time to informal care, market work, and leisure. We use the estimates to decompose the effects of adult children's opportunity costs, quality of care, and caregiving burden on their propensities to provide informal care. We also simulate the effects of a broad range of policies of current interest. © (2009) by the Economics Department of the University of Pennsylvania and the Osaka University Institute of Social and Economic Research Association.

Cohabitation, marriage, and divorce in a model of match quality

The objective of this research is to further our understanding of how and why individuals enter and leave coresidential relationships. We develop and estimate an economic model of nonmarital cohabitation, marriage, and divorce that is consistent with current data on the formation and dissolution of relationships. Jovanovic's (Journal of Political Economy 87 (1979), 972-90) theoretical matching model is extended to help explain household formation and dissolution behavior. Implications of the model reveal what factors influence the decision to start a relationship, what form this relationship will take, and the relative stability of the various types of unions. The structural parameters of the model are estimated using longitudinal data from a sample of female high school seniors from the United States. New numerical methods are developed to reduce computational costs associated with estimation. The empirical results have interesting interpretations given the structural model. They show that a significant cause of cohabitation is the need to learn about potential partners and to hedge against future bad shocks. The estimated parameters are used to conduct several comparative dynamic experiments. For example, we show that policy experiments changing the cost of divorce have little effect on relationship choices.

Survival models of community tenure and length of hospital stay for the seriously mentally ill : a 10-year perspective

Objective: To examine the effects of personal and community characteristics, specifically race and rurality, on lengths of state psychiatric hospital and community stays using maximum likelihood survival analysis with a special emphasis on change over a ten year period of time. Data Sources: We used the administrative data of the Virginia Department of Mental Health, Mental Retardation, and Substance Abuse Services (DMHMRSAS) from 1982-1991 and the Area Resources File (ARF). Given these two sources, we constructed a history file for each individual who entered the state psychiatric system over the ten year period. Histories included demographic, treatment, and community characteristics. Study Design: We used a longitudinal, population-based design with maximum likelihood estimation of survival models. We presented a random effects model with unobserved heterogeneity that was independent of observed covariates. The key dependent variables were lengths of inpatient stay and subsequent length of community stay. Explanatory variables measured personal, diagnostic, and community characteristics, as well as controls for calendar time. Data Collection: This study used secondary, administrative, and health planning data. Principal Findings: African-American clients leave the community more quickly than whites. After controlling for other characteristics, however, race does not affect hospital length of stay. Rurality does not affect length of community stays once other personal and community characteristics are controlled for. However, people from rural areas have longer hospital stays even after controlling for personal and community characteristics. The effects of time are significantly smaller than expected. Diagnostic composition effects and a decrease in the rate of first inpatient admissions explain part of this reduced impact of time. We also find strong evidence for the existence of unobserved heterogeneity in both types of stays and adjust for this in our final models. Conclusions: Our results show that information on client characteristics available from inpatient stay records is useful in predicting not only the length of inpatient stay but also the length of the subsequent community stay. This information can be used to target increased discharge planning for those at risk of more rapid readmission to inpatient care. Correlation across observed and unobserved factors affecting length of stay has significant effects on the measurement of relationships between individual factors and lengths of stay. Thus, it is important to control for both observed and unobserved factors in estimation.

The effects of rurality on mental and physical health

The effects of rurality on physical and mental health are examined in analyses of a national dataset, the Community Tracking Survey, 2000-2001, that includes individual level observations from household interviews. We merge it with county level data reflecting community resources and use econometric methods to analyze this multi-level data. The statistical analysis of the impact of the choice of definition on outcomes and on the estimates and significance of explanatory variables in the model is presented using modern econometric methods, and differences in results for mental health and physical health are evaluated. © 2010 Springer Science+Business Media, LLC.

Measuring child work and residence adjustments to parents' long-term care needs

This article estimates the effects of various parent and child characteristics on the choice of care arrangement of the parent, taking into account the potential endogeneity of some of the child characteristics. Three equations are estimated: a care choice equation, a child location equation, and a child work equation. Results suggest a hierarchy of family decision making; child locations affect the care decision, which affects child work decisions. The results also question previous research attempting to explain causes of secular trends in long-term care.

Imputing a continuous income variable from a bracketed income variable with special attention to missing observations

This paper proposes a method, based on polychotomous discrete choice methods, to impute a continuous measure of income when only a bracketed measure of income is available and for only a subset of the obsevations. The method is shown to perform well with CP5 data. © 1991.

Rules of thumb for comparing multinomial logit and multinomial probit coefficients

A rule of thumb is suggested for comparing multinomial logit coefficients with multinomial probit coefficients in the special case where the normal errors are distributed N(0,1). The rule is a generalization of the '1.6' rule for comparing logit and probit coefficients. © 1989.

Approximate solutions to stochastic dynamic programs

This paper examines the properties of various approximation methods for solving stochastic dynamic programs in structural estimation problems. The problem addressed is evaluating the expected value of the maximum of available choices. The paper shows that approximating this by the maximum of expected values frequently has poor properties. It also shows that choosing a convenient distributional assumptions for the errors and then solving exactly conditional on the distributional assumption leads to small approximation errors even if the distribution is misspecified. © 1997 Cambridge University Press.

Shortages of rural mental health professionals

This study presents a conceptual model of the supply and demand for mental health professionals. It uses national data to profile differences in the supply of mental health professionals in different types of rural and urban areas. It contrasts the availability of general health and mental health professionals. It examines shortage areas identified in 2000 and their related community characteristics. Because of the absence of data on a national level to describe many types of mental health professionals state licensure data for one state were used to show the volume and distribution of these practitioners. To improve rural mental health service delivery it will be necessary to implement system changes to promote the increased availability, competency, and support of rural health professionals. Copyright 2003, Elsevier Science (USA). All rights reserved.