The use and prevalence of JEL code categorization is wide in the field of economics, but what do JEL code classifications actually tell us? And are they used with consistency by academics in the field? Utilizing a data set of articles published in the American Economic Review from 1990 to 2008, we investigate whether there is heterogeneity in JEL codes assignments between authors and editors. We find that there is. A secondary goal of this paper is to survey overall thematic trends in JEL code usage over the past four and a half decades. One result is that JEL category M: Business Economics, in particular, appears to be thematically and spatially distinct from much of the rest of the published literature in the top general interest journals in the field.