Hartman, N., Williamson, A., Sojka, B., et al. (2009). Predicting Resource Use at Mass Gatherings Using a Simplified Stratification Scoring Model. (Abstract only.) The American Journal of Emergency Medicine. 27(3): 337-43.
The authors tested a classification system that stratifies events based on weather, number in attendance, presence of alcohol, demographic in attendance, and crowd intentions to predict medical needs at mass gatherings. The system predicted needs better for "minor" and "intermediate" events (less so for "major" events).