Attenuated Heterogeneity in Fixed-Effects Causal Forests, and a Cross-Fitted Correction
固定效应因果森林中的异质性衰减及交叉拟合校正
Causal forests that estimate conditional average treatment effects by averaging honest leaf-level effects across trees are widely used in fixed-effects panel settings. We show that this averaging systematically attenuates the estimated heterogeneity: the raw prediction behaves like a + b*tau(x) with slope b < 1, so the spread of the CATEs is compressed toward the average effect, and the additive recentering used to report an unbiased average treatment effect does not fix it.…