Using Compustat to measure industry concentration in the U.S. is problematic. Popular approximations of the Herfindahl Index based on this data set have a vanishingly low correlation with the more comprehensive Census measure. As a result, major variables of interest in corporate finance show markedly different correlations with these indicators, which can lead to a breakdown of regression results. This confirms findings of an earlier article that has been ignored by recent empirical studies. I show that Census concentration ratios are excellent measures and provide a newly compiled data set based on all concentration data ever produced by the Department of Commerce – eliminating the need to use the convenient but flawed Compustat files.