Care‐giver advice as a preventive measure for drinking during pregnancy: zeros, categorical outcome responses, and endogeneity
研究了产前看护者建议对孕妇饮酒行为的影响，采用修正的两部分模型处理零消费和分类数据，并纠正建议变量的内生性，发现忽略内生性会得出误导性结论。
We conduct an empirical investigation of the impact of prenatal care-giver advice on alcohol consumption by pregnant women. In the design of the model and estimator, we pay particular attention to three aspects of the data. First, a large proportion of pregnant women do not drink at all. To accommodate this aspect of the sample we base the essential formulation of the model on the modified version of the two-part approach of Duan et al. (Journal of Business and Economic Statistics 1983; 1: 115-126.) suggested by Mullahy (Journal of Health Economics 1998; 17: 247-281.). Second, in the survey that we analyze (the 1988 National Maternal and Infant Health Survey - NMIHS), respondents were only required to report their consumption up to a specified range of values (e.g. 1-2 drinks per week, 2-5 drinks per week, and so on). For this reason, the model is cast in the grouped regression framework of Stewart (Review of Economic Studies 1983; 50: 141-149.). Third, the binary physician advice variable is likely to be endogenous and the econometric specification explicitly accounts for this possibility. To summarize the results, we find that failing to account for endogeneity leads to the counterintuitive conclusion that advice has a positive and statistically significant influence on drinking during pregnancy. When the model is extended to allow for potential endogeneity, we find that advice has a negative and statistically significant impact.