Influence of the size of the data set on the astrophysical constraints derived from the clustering analysis. Left column: values of the “clustering similarity”, , for all pairs of parameters (n_s,δ), obtained from the analysis of data sets with an energy threshold E_min = 60 EeV, containing respectively (from top to bottom) 50, 250 and 1000 events, each being a typical realization of the reference model , δ = 5°), indicated by the white cross. For all models considered here, a uniform distribution of the sources was assumed. Right column: confidence contours extracted from the same data sets.