Forecasting the outputs of dynamic systems develops a richer understanding of relevant inputs and their interrelationships than merely observing them ex post. Academic business simulations foster students' development of this critical competency, but learning outcomes can be significantly augmented with relatively simple, complementary exercises in forecasting. We introduce an in-class forecasting exercise that is easily added to simulations or in any course where students gain from untangling the determinants of quantitative outcomes. The exercise also enhances opportunities for team-building and spirited competition. Implementation details, evidence of effectiveness, and implications are discussed.