Effect of population size on rank distribution. 780 marker combinations have been evaluated for each distribution. The black dashed curve is the hypothetical null distribution. The boxes on the right of each set of curves indicate the ratio of affected and non-affected markers for each curve. If the ratio is 0.5, every marker combination has some induced survival effect. In the left panel population size is 10,000, in the middle panel 1,000, and in the right panel 100.