Title: Estimation and Inference for Moments of Ratios with Robustness against Large Trimming Bias,
Abstract: Empirical researchers often trim observations with small denominator A when
they estimate moments of the form E[B/A]. Large trimming is a common practice
to mitigate variance, but it incurs large trimming bias. This paper provides a
novel method of correcting large trimming bias. If a researcher is willing to
assume that the joint distribution between A and B is smooth, then a large
trimming bias may be estimated well. With the bias correction, we also develop
a valid and robust inference result for E[B/A].