where f is the distribution taken from the data, g is the approximate distribution of the same feature recovered from the model over many simulated years and p is a vector of model parameters. (See the electronic supplementary material for implementation.) The overall measure of goodness of fit used is the unweighted sum of the information distances for AAR and duration. We explore parameter space to identify regions where model behaviour most closely resembles empirical patterns. Although a simplified description of the epidemiological and evolutionary mechanisms of human influenza, our model nevertheless incorporates a substantial number of parameters. We focus on the following groupings: