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arXiv 2012.10790econ.EMcs.CYcs.LG
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利用数据挖掘变量实现可靠的因果推断:测量误差问题的随机森林方法

Achieving Reliable Causal Inference with Data-Mined Variables: A Random Forest Approach to the Measurement Error Problem

University of Minnesota, Carlson School of Management(明尼苏达大学卡尔森管理学院)

Mochen Yang, Edward McFowland, Gordon Burtch, Gediminas Adomavicius

摘要:

将机器学习与计量经济学分析相结合在研究和实践中变得越来越普遍。一个常见的实证策略涉及应用预测建模技术从现有数据中“挖掘”感兴趣的变量,然后将这些变量纳入计量经济学框架,目的是估计因果效应。最近的工作强调,由于机器学习模型的预测不可避免地是不完美的,基于预测变量的计量经济学分析可能会因测量误差而产生偏差。我们提出了一种新的方法来减轻这些偏见,利用集成学习技术称为随机森林。我们建议采用随机森林不仅用于预测,而且用于生成工具变量,以解决嵌入在预测中的测量误差。随机森林算法在由一组树组成时表现最好,这些树在其预测中各自准确,但也会犯“不同”的错误,即,具有弱相关的预测误差。一个关键的观察是,这些属性是密切相关的有效工具变量的相关性和排除要求。我们设计了一个数据驱动的程序来从随机森林中选择个体树的元组,其中一棵树作为内生协变量,其他树作为其工具。仿真实验表明,所提出的方法在减轻估计偏差和其优越的性能比三种替代方法的偏差校正的有效性。

英文摘要:

Combining machine learning with econometric analysis is becoming increasingly prevalent in both research and practice. A common empirical strategy involves the application of predictive modeling techniques to 'mine' variables of interest from available data, followed by the inclusion of those variables into an econometric framework, with the objective of estimating causal effects. Recent work highlights that, because the predictions from machine learning models are inevitably imperfect, econometric analyses based on the predicted variables are likely to suffer from bias due to measurement error. We propose a novel approach to mitigate these biases, leveraging the ensemble learning technique known as the random forest. We propose employing random forest not just for prediction, but also for generating instrumental variables to address the measurement error embedded in the prediction. The random forest algorithm performs best when comprised of a set of trees that are individually accurate in their predictions, yet which also make 'different' mistakes, i.e., have weakly correlated prediction errors. A key observation is that these properties are closely related to the relevance and exclusion requirements of valid instrumental variables. We design a data-driven procedure to select tuples of individual trees from a random forest, in which one tree serves as the endogenous covariate and the other trees serve as its instruments. Simulation experiments demonstrate the efficacy of the proposed approach in mitigating estimation biases and its superior performance over three alternative methods for bias correction.

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