یک الگوی اقتصاد سنجی از نهاده و خروجی های تولد برای بومیان آمریکا

This paper presents a new model of the birth process of Native Americans with seven endogenous variables: four birth inputs maternal smoking (S), drinking (D), prenatal care (PC), and weight gain (WG), and three birth outputs gestational age (G), birth length (BL), and birth weight (BW). The model is a seven-equation simultaneous model with three endogenous dummies S, D, and PC. The data are taken from the National Longitudinal Survey of Youth (NLSY). We find that the four birth inputs are determined jointly and dependently among S, D, and PC, but independently of WG. S has negative systematic correlation with G. D and PC appear to have no sizeable systematic effect on G, BL, or BW. Except for the sizeable and positive correlation between the unexplained parts of S and G, there seem to be no unexplained common effects between the birth inputs and outputs. Moreover, G appears dependent on the exogenous size of the mother. BL is affected by the inputs mainly through WG. BW is affected by the inputs through their effects on G. Except for maternal weight, there is little correlation between the remaining exogenous variables and BW. Finally, the predictive density of BW for a typical pregnancy gives a mean weight of View the MathML source.

This paper is the first of a series by us (Li and Poirier 2000, Li and Poirier 2001a, Li and Poirier 2001b and Li and Poirier 2002) analyzing birth weight (BW) and related birth outcomes. The model has its origins in Poirier (1998) and we extend the estimation procedures discussed in Chib and Greenberg (1998) and Li 1996 and Li 1998. BW is probably the single most important indicator of infant health (Institute of Health, 1985). It is also a significant predictor of infant mortality, morbidity, coronary heart disease, and learning disabilities later in life (Poirier, 1998). The vast majority of studies on BW, particularly in the biomedical literature are single-equation models that ignore the simultaneity issues, a notable exception is Permutt and Hebel (1989). An important contribution of this study is to address the simultaneity issue head on. Our new model for the birth process is a nonlinear simultaneous equations model with the following features: (1) triangular coefficients of endogenous variables matrix, (2) mixed unlimited and limited (dichotomous) dependent variables, (3) zero restrictions on elements of both coefficients of endogenous variables matrix and coefficients of exogenous variables matrix, and (4) normal residuals. Existing work with a Bayesian orientation sharing some of these features are Chib and Greenberg (1998) and Li 1996 and Li 1998. Chib and Greenberg (1998) concerns multivariate probit models. As in Chib and Greenberg (1998), diagonal elements of the variance–covariance matrix corresponding to dichotomous dependent variables are restricted to be unity and the Metropolis update (Chib and Greenberg, 1995) we take in this paper for each block of the variance–covariance matrix is essentially the same as Chib and Greenberg (1998). The model in Li 1996 and Li 1998 has features of and , and limited dependent variables (mixed dichotomous and censored). The paper proceeds as follows. In Section 2 we introduce the data. In Section 3 we discuss our modeling framework and the prior distribution. We present computational details in Section 4 and report empirical results in Section 5. Some concluding remarks are offered in Section 6.