Optimization of volunteer task assignments to improve volunteer retention and nonprofit organizational performance

Deploying the skills and experiences of nonprofit employees and volunteers is challenging due to resource constraints on nonprofit organizations and the salient characteristics of volunteer labor. This research introduces an integer linear program to make volunteer and employee task assignments for a planned nonprofit program that captures the impact of task assignments on volunteer retention in future periods. Assignments are made to balance the need for urgency of current tasks, organizational task preferences, volunteer trainings, and volunteer preferences (which impact retention). The deterministic optimization model is evaluated using a computational design of experiments with a food bank use case and a simulation model that incorporates uncertainty in volunteer preferences and retention. The developed model, which captures the impact of task assignment on expected volunteer retention, is compared to a simpler benchmark that ignores task assignment's impact on volunteer retention and instead makes assignments maximizing the organization's preferences. The proposed approach is found to be beneficial to nonprofits, even when an NPO has uncertainty in their estimates for volunteer preferences and volunteer retention threshold values.