Because our focus is on early retrieval of actives, we chose these top models based on mean normalized enrichment factor at 1% (NEF 1% ) performance (Section 4.4). Figure To further explore why the ensemble methods did not improve the performance over the best individual models (Figures and), we examined the overlap in actives retrieved between the ensembles and top models (Tables ). Although the ensembles found some actives not prioritized by the best RF-C model, the RF-C found many more actives, leading to better performance. We note several methodological improvements that could improve the ensemble performance in Appendix A.8.