Cumulative X-ray luminosity function of SNRs in Local Group galaxies. See text for details and references on how L_X was measured for each sample. The brightest SNR in each galaxy is marked by a dot. The thin dotted lines are nonlinear least-square fits of a power law (N( >L_X) ∝ L_X^α). Slopes α are given in the legend. These fits are only used to characterise the slopes and illustrate the differences between galaxies; they do not represent a physical fit of the population.