Browsing by Subject "Endogeneity"

Now showing 1 - 2 of 2
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    Perceived access barriers to conventional medicine and the use of complementary and alternative medicine (CAM)
    (2008-08) Yu, Tzy-Chyi
    Objectives. Little attention has been paid to the connection between perceived access barriers to conventional medicine and CAM usage. The purpose of this dissertation is to quantitatively evaluate the associations between perceived access barriers to conventional medicine and CAM usage using population data. Method. This is a cross-sectional study using the 1999 and 2002 National Health Interview Survey. The target population is U.S. civilians age 18 to 64. The outcome variable is CAM usage classified into homogenous subgroups. Perceived access barriers to conventional medicine are grouped into distinct dimensions including affordability, accommodation, or accessibility. To deal with potential selection problems related to perceived access barriers to conventional medicine, recursive bivariate probit models are utilized to test the impact of individual perceived access barriers on CAM usage after controlling confounders. Moreover, multivariate probit and Boolean probit models are used to evaluate all three distinct perceived access barrier dimensions simultaneously on CAM usage. Results. In general, perceived access barriers to conventional medicine are positively related to CAM usage, to varying degrees. The various relationships found in this dissertation between each perceived access barriers to conventional medicine and CAM subgroup usage show a clear picture that neither perceived access barriers to conventional medicine nor CAM is homogenous. Moreover, several bivariate probit models are significant, indicating that perceived access barriers to conventional medicine are endogenous in these models. It can be seen from model comparison that serious biases arise from simple probit models when these variables of interest are endogenous. Furthermore, the impact of three perceived access barrier dimensions on CAM use differs in multivariate probit and Boolean probit models, each of which has its assumptions, as such strengths and limitations. Conclusions. Ignoring the endogenous nature of perceived access barriers to conventional medicine will bias estimates of the relationships between perceived access barriers to conventional medicine and CAM usage. People who perceive access barriers are likely to use CAM, especially perceived accommodation access barriers. These access barriers should be addressed to ensure that people have adequate access to health care services, both conventional and alternative, to improve their health.
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    Three Essays On Political Economy And The Methods
    (2020-05) Wang, Yu
    This dissertation consists of three essays regarding political economy and the theoretical discussion of two empirical methods. Chapter 2 (Essay 1) discusses how the introduction of local direct elections, by providing local information, facilitates the fulfillment of the meritocratic selection of local leaders. Using the Bayesian framework, this paper finds that because local residents, the voters, communicate with the local leader candidates of more times than upper officials do, local residents infer each local leader candidate’s virtue or capacity more accurately and precisely. This paper then shows that due to the higher accuracy, the expectation of the competence (a weighted average of virtue and capacity) of the elected local leader is higher than that of the appointed leader; due to the higher precision, the variance of the competence of the elected local leader is lower than that of the appointed leader. Chapter 3 (Essay 2) discusses the lagged IV method, namely using the lagged endogenous explanatory variable as its instrumental variable (IV). This paper starts with a conceptual framework, and then conducts the numerical analysis. It shows that when the lagged IV only violates the independence assumption, the lagged IV estimate is consistent, and has lower bias than the OLS estimate; however, when the lagged IV violates both the independence assumption and the exclusion restriction, the lagged IV estimate is inconsistent, and has much higher bias than the OLS estimate. The simulation results support the numerical analysis. Chapter 4 (Essay 3) discusses the spatially lagged IV method, namely using the spatially lagged endogenous explanatory variable, namely the spatial weighting matrix, as its instrumental variable (IV). This paper introduces the spatially local average treatment effect (SLATE) theorem, which consists of two key properties: the spatial independence assumption and the spatial exclusion restriction. This paper demonstrates that when the spatially lagged IV satisfies the spatial independence assumption and the spatial exclusion restriction, its estimate is unbiased and consistent. Even if the treatment has multiple waves of implementation, the spatially lagged IV is still valid.