ppmlhdfe: Fast Poisson Estimation with High-Dimensional Fixed Effects
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PPMLHDFE: Fast Poisson Estimation with High-Dimensional Fixed Effects
\affil[1]{Federal Reserve Board, [email removed]}
\affil[2]{Banco de Portugal, [email removed]}
\affil[3]{University of Richmond, [email removed]}
abstractIn this paper we present {\tt ppmlhdfe}, a new Stata command for estimation of (pseudo) Poisson regression models with multiple high-dimensional fixed effects (HDFE). Estimation is implemented using a modified version of the iteratively reweighted least-squares (IRLS) algorithm that allows for fast estimation in the presence of HDFE. Because the code is built around the {\tt reghdfe} package, it has similar syntax, supports many of the same functionalities, and benefits from {\tt reghdfe}'s fast convergence properties for computing high-dimensional least squares problems. Performance is further enhanced by some new techniques we introduce for accelerating HDFE-IRLS estimation specifically. {\tt ppmlhdfe} also implements a novel and more robust approach to check for the existence of (pseudo) maximum likelihood estimates.