工具變數法在經濟學與會計學的應用

Applications of Instrumental Variable Method in Economics and Accounting

在實證研究中，我們往往找出了一些變數間的相關性，卻難以界定變數間的因果關係。許多經濟學家使用工具變數法，解決主要解釋變數間的內生性問題。在我們所關心，想估計的效果具有異質性的時候，我們使用工具變數所估計出來的效果，與平均處置效果可能會有相當大的差異。在這篇文章中，我們以簡單的例子，介紹工具變數所估計出來的局部平均處置效果（local average treatment effects, LATE）與平均處置效果（average treatment effect, ATE）之間的差別。最後並介紹在經濟學與會計學中，我們常見的一些工具變數。 Identifying causal relationship between variables could be challenging in empirical studies. Many economists apply instrumental variable method to solve indigeneity of variables of interest. When the causal effect we are interested in is heterogeneous among the population, the estimated effect via instrumental variable method could be far from average treatment effect (ATE). Instead of ATE, we will have local average treatment effect (LATE) by implementing instrumental method. In this study, we will illustrate the difference between LATE and ATE. We will also illustrate applications of the instrumental method in economics and accounting.

Identifying causal relationship between variables could be challenging in empirical studies. Many economists apply instrumental variable method to solve indigeneity of variables of interest. When the causal effect we are interested in is heterogeneous among the population, the estimated effect via instrumental variable method could be far from average treatment effect (ATE). Instead of ATE, we will have local average treatment effect (LATE) by implementing instrumental method. In this study, we will illustrate the difference between LATE and ATE. We will also illustrate applications of the instrumental method in economics and accounting.