Gravity model estimation: fixed effects vs. random intercept Poisson pseudo-maximum likelihood

The standard Anderson and van Wincoop gravity model has typically been estimated using a fixed-effects approach. However, a fixed-effects approach has a major drawback: it does not allow for the estimation of exporter- and importer-invariant variables. Thus, at least in a cross-sectional context, economically relevant variables such as exporter and importer gross domestic product are disregarded. We propose a random intercept model to address this gap. For large datasets, this approach not only provides identical estimates like a fixed-effects approach, but also allows for the estimation of exporter- and importer-invariant variables.