We observe a great deal of heterogeneity in the manner in which author orderings are assigned both across and within academic markets. To better understand this phenomenon, we develop and analyze a stochastic model of author orderings. In our model, authors work equally hard to obtain priority in listings but linal contributions arc stochastic. Further, research outlets differ in their quality hurdles. In this setting, our simulation results are consistent with two empirical regularities. First, we lind that the rate of alphabetization increases with the stringency with which papers are accepted for publication. Second, conditional on clearing the publication hurdle, quality increases with alphabetization. These findings arise because increases in the publication hurdle make it more likely that authors will exceed this threshold only when both contribute a high amount. This, in turn, leads to roughly equal contributions I alphabetization I and also generates a positive correlation between alphabetization and quality.