Predicted regional-level between-farm association frequency extrapolated to farms recorded in the Great Britain Poultry Register. Regional average probabilities of (a) large versus medium and (b) large versus small between-farm association frequencies (blue circles), following extrapolation of network information to the Great Britain Poultry Register (n = 3009 farms). Error bars represent 95% confidence intervals generated from 1000 stochastic simulations of randomly assigning each farm to a small, medium or large between-farm association frequency group. Black triangles represent proportions of farms within these categories observed from the Poultry Network Database (n = 662 farms). (c) Geographical clustering of the regional predicted probabilities represented by their corresponding colours (note: Scotland and Wales were considered distinct from the other regions). W = Wales; S = Scotland; L = Greater London; WM = West Midlands, SW = South West, EM = East Midlands, NE = North East, E = East, Y = Yorkshire, NW = North West and SE = South East of England.