Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
This paper compares three types of standard errors for optimal minimum distance (OMD) estimator where the structural parameter is recovered from the reduced form parameters estimated by a two-step GMM estimator. We demonstrate that the naive standard errors are severely biased and cause over-rejection, while the OMD estimator based on the bias-corrected variance matrix by Windmeijer (2005) and newly derived variance estimator yield much more accurate inference.