David K. Guilkey

Binary outcomes and endogenous explanatory variables: Tests and solutions with an application to the demand for contraceptive use in tunisia

Many demographic studies examine discrete outcomes, and researchers often suspect that some of the explanatory variables may be influenced by the same unobserved factors that determine the discrete outcome under examination. In linear models, the standard solution to this potential endogeneity bias is an estimator such as two-stage least squares. These methods have been extended to models with limited dependent variables, but there is little information on the performance of the methods in the types of data sets typically used in demographic research. This paper helps to fill this gap. It describes a simple analytic framework for estimating the effects of explanatory variables on discrete outcomes, which controls for the potential endogeneity of explanatory variables. It also discusses tests for exogeneity and joint determination of the outcomes and the explanatory variables. It summarizes the results of a Monte Carlo study of the performance of these techniques and uses these results to suggest how researchers should approach these problems in practice. We apply these methods to the examination of the impact of fertility intentions on contraceptive use, based on data from the 1988 Tunisia Demographic and Health Survey.

A Comparison of the Performance of Three Flexible Functional Forms

When selecting a functional form for use in empirical work, one is confronted by a choice between forms that exhibit good behavior globally and those that possess flexibility. Relatively simple forms, such as Cobb-Douglas and CES, satisfy certain regularity conditions globally, but the very simplicity that guarantees global good behavior also prevents such forms from modelling very sophisticated technologies. On the other hand, relatively complex forms having the flexibility to model fairly sophisticated technologies have been developed, but their very flexibility prevents them from being well-behaved globally. The current trend is clearly toward the development and use of flexible forms which, although not globally well-behaved, may nonetheless satisfy the desired regularity conditions over a range of observations that contain or intersect the set of sample observations. In light of their inability to satisfy regularity conditions globally, and in light of the substantial econometric sophistication required in their estimation, it is worthwhile investigating just how well various flexible forms do model technology. This can be accomplished in a number of ways. Berndt, Darrough and Diewert [1977] simply fitted three flexible forms translog, generalized Leontief and generalized Cobb-Douglas to postwar Canadian expenditure data, and found the translog model to be preferred on Bayesian grounds a posteriori. Applebaum [1979] and Berndt and Khaled [1979] developed generalized Box-Cox forms that contain the translog, generalized Leontief, and generalized square root quadratic forms as special or limiting cases. Using 1929-1971 U. S. manufacturing data, Applebaum found that the generalized Leontief and generalized square root quadratic forms the best representations for the primal and dual specifications of technology. Using 1947-1971 U. S. manufacturing data, Berndt and Khaled were able to reject the generalized square root quadratic restriction, but unable to reject the generalized Leontief restriction; tests concerning the translog restriction were inconclusive. A difficulty with this empirical approach is that the true technology is unknown. Evaluating the performance of flexible forms on the basis of how well they fit observed data is useful if interest centers on the data, but may be misleading if

Estimation and testing in the random effects probit model

Abstract This paper examines the finite-sample properties of the random effects probit estimator in comparison to the standard probit estimator and the standard probit estimator with a corrected asymptotic covariance matrix. The Monte Carlo experiment considers data-generating processes consistent with longitudinal data and also data from sample surveys. The probit estimator with corrected asymptotic covariance matrix works surprisingly well over a wide range of parametric configurations and is recommended as long as an estimate of the error correlation is not of high importance

The Demand for Primary Health Care Services in the Bicol Region of the Philippines

Mortality is assumed to be strongly reduced by medical care however the effects of medical services on health are often underestimated because some of the same factors which lead to an increased demand for primary health care (PHC) services are also associated with increased morbidity and mortality. Consequently understanding the determinants of the demand for medical services is important for evaluating health outcomes. This paper estimates the parameters of a simple model of the demand for health services using data from the Bicol Multipurpose Survey data from the Philippines. The parameters of the demand for key components of PHC--outpatient prenatal delivery well-child and infant immunizations--are estimated. Findings suggest that the quality of the care may be very important but that economic factors as deterrents to using medical care--inaccessibility cash costs and lack of income--may not be of paramount importance. Finally it is shown that the provision of free services in rural areas may not insure that the services reach the poorest people. (authors modified)

Food price and diet and health outcomes: 20 years of the CARDIA Study.

BACKGROUND Despite surging interest in taxation as a policy to address poor food choice, US research directly examining the association of food prices with individual intake is scarce. METHODS This 20-year longitudinal study included 12 123 respondent days from 5115 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Associations between food price, dietary intake, overall energy intake, weight, and homeostatic model assessment insulin resistance (HOMA-IR) scores were assessed using conditional log-log and linear regression models. RESULTS The real price (inflated to 2006 US dollars) of soda and pizza decreased over time; the price of whole milk increased. A 10% increase in the price of soda or pizza was associated with a -7.12% (95% confidence interval [CI], -63.50 to -10.71) or -11.5% (95% CI, -17.50 to -5.50) change in energy from these foods, respectively. A

The changing impact of religion on the sexual and contraceptive behavior of adolescent women in the United States

1.00 increase in soda price was also associated with lower daily energy intake (-124 [95% CI, -198 to -50] kcal), lower weight (-1.05 [95% CI, -1.80 to -0.31] kg), and lower HOMA-IR score (0.42 [95% CI, -0.60 to -0.23]); similar trends were observed for pizza. A

Community and contraceptive choice in rural Thailand: a case study of Nang Rong.

1.00 increase in the price of both soda and pizza was associated with greater changes in total energy intake (-181.49 [95% CI, -247.79 to -115.18] kcal), body weight (-1.65 [95% CI, -2.34 to 0.96] kg), and HOMA-IR (-0.45 [95% CI, -0.59 to -0.31]). CONCLUSION Policies aimed at altering the price of soda or away-from-home pizza may be effective mechanisms to steer US adults toward a more healthful diet and help reduce long-term weight gain or insulin levels over time.

Cohort Profile: The Cebu Longitudinal Health and Nutrition Survey

This study examined the relationship between religion and adolescent sexual and contraceptive behaviors in the US. Data were obtained from the 1982 and 1988 Cycles of the National Survey of Family Growth among a sample of women 15-44 years of age. Models examined the determinants of risk of intercourse and contraceptive use only for women who were virgins at the start of the 4-year period preceding each survey. Findings indicate few religious differences in the likelihood of virginity retention among Whites in 1982. By 1988 there were large religious differences in risk of intercourse. White fundamentalists were able to reverse trends and increase the likelihood of retaining virginity. Among fundamentalist Blacks 50% were more likely to remain virgins regardless of time period. Denomination influenced contraceptive choice at first intercourse and the effects differed by race. White Catholics and fundamentalists were less likely to use any method at first intercourse than other religions. Most women who used a method relied on condoms at first intercourse. Fundamentalists were the most likely to use the pill. Black Catholics were more likely to use the pill and Blacks of other religions tended to use the condom. 62% of Whites and 60% of Blacks aged 15-19 years used contraception especially the pill at the most recent intercourse. 60% of White adolescents and only 46% of Blacks used contraception at first intercourse. Denomination or attendance had little effect on current contraceptive behavior among White teens. Findings suggest that the effects of denomination on the risk of intercourse and contraceptive use initially were not maintained after first intercourse.

Modeling Food Consumption Decisions as a Two-Step Process

This paper blends quantitative with qualitative data in an investigation of community and contraceptive choice in Nang Rong, Thailand. Specifically, it develops an explanation of 1) method dominance within villages, coupled with 2) marked differences between villages in the popularity of particular methods. The quantitative analysis demonstrates the importance of village location and placement of family planning services for patterns of contraceptive choice. The qualitative data provide a complementary perspective, emphasizing the importance of social as well as physical space and giving particular attention to the structure of conversational networks.

Accessibility, quality of care and prenatal care use in the Philippines

The Cebu Longitudinal Health and Nutrition Survey (CLHNS) was originally conceptualized as an interdisciplinary study of infant-feeding patterns, particularly the overall sequencing of feeding events (milks and complementary foods), the factors affecting feeding decisions and how feeding patterns affect the infant, mother and household. The idea was to study these topics within as natural a setting as possible and to analyse how infant-feeding decisions interacted with social, economic and environmental factors to affect health, nutritional, demographic and economic outcomes. The study was subsequently expanded to cover a wide range of maternal and child health and demographic issues that could be well studied using a prospective, community-based sample. The study was initially the product of collaboration among researchers at the Carolina Population Center at the University of North Carolina at Chapel Hill (led by B.M.P. with J.S.A. and D.K.G.), The Office of Population Studies Foundation at the University of San Carlos in Cebu, Philippines (led by the late Director Wilhelm Fleiger) and the Nutrition Center of the Philippines (led by Florentino Solon). L.S.A. took the lead for follow-up surveys beginning in 1990. Later, the study team was expanded to include researchers presently at the Northwestern University (C.W.K. and T.M.D.) and Johns Hopkins University (M.J.H.). The study was initiated with cooperation and approval from the Cebu Department of Health. The CLHNS website includes a full list of investigators and their affiliations. The CLHNS was one of the first large-scale, population-based surveys designed with a conceptual framework in mind. The guiding framework was adapted from Mosley and Chen’s health determinants model, which posits that underlying community-, householdand individual-level variables affect a set of proximate health behaviours which, in turn, influence health outcomes such as growth and infectious disease morbidity and mortality. The study was designed by a highly interdisciplinary group of economists, sociologists, nutritionists, demographers and physicians. The CLHNS has been funded by a large number of government and non-government organizations (listed in the Funding section).