Differences in employee evaluations due to gender bias may be small in any given rating cycle, but these small differences may accumulate to produce large disparities in the number of women and men promoted to the top of an organization. A highly cited simulation by Martell et al. (1996) demonstrates this cumulative advantage process in a multi-level organization. We replicated this simulation to uncover important details about its operating assumptions, and we extended the simulation to examine a range of variables that may impact the cumulative effects of gender bias. The replication revealed that the male cumulative advantage in the Martell et al. simulation requires (a) decades of promotion cycles to produce, (b) constant mean differences in the performance ratings of women and men but equal within-group variances, and (c) attrition that occurs randomly at a low and constant rate. Our extended simulation demonstrates that (a) the cumulative effects of gender bias are higher when the attrition rate is lower, (b) gender biases are mitigated when attrition is more strongly tied to good or poor performance, and (c) the cumulative effects of mean gender differences in performance ratings can often be smaller than the cumulative effects of variance differences between gender subgroups. These results suggest that talent development and recognition of high performers will often have a greater positive impact on female representation at top levels of a firm than programs aimed at reducing bias in employee evaluations. We encourage additional simulation work that further explores the dynamics of cumulative advantage in employment settings.