Existing Models  Type 1: Classical time-series techniques  Fit trend, seasonality and stationary components to time-series [Enders & Sandler]  Quadratic or cubic trend = 4 parameters, seasonality = 3, stationary part = 1  Fit lagged value of endogenous variables, and other variables [Barros]  8 or more model parameters  Key Theme: Good-to-acceptable fit for time-series at the cost of large number of parameters in a model with complicated dependencies  Type 2: Group-based trajectory analysis  Identify cases with similar development trends [Nagin]  Cox proportional hazards model + logistic regression methods for model selection [LaFree, Dugan & co-workers]  Key Theme: Contagion theoretic viewpoint  Current activity of group is influenced by past history of group  Attacks are clustered 5
{}