Comparison of divergence and polymorphism data in different gene sets. The data shown are for genes in which Dn, Ds, Pn and Ps ≠ 0 and Pn + Ps ≥ 4 (2,545 genes in the complete dataset; 109 human accelerated genes; 98 human branch-site (BS) test genes). The area within the box contains 50% of the data; the horizontal line is the median; small circles represent outliers (5%). The y-axis (FI) has been cut at FI = 5. We performed Mann–Whitney-Wilcoxon tests against the background (All genes) distribution: *p < 0.05; **p < 0.01; ***p < 0.001.