We repeated this analysis for GWA studies where at least one locus had reached genome-wide significance for any of three quantitative traits: height (8, 11, 25, 43, 54, 57, 72, 84, 88, 92, 94, 95), lipid levels (triglycerides, HDL-cholesterol and LDL-cholesterol; (5, 10, 16, 45, 46, 49, 51, 58, 91, 98)) and blood pressure (systolic and diastolic blood pressure (32, 47, 59, 74)). For multistage studies (where top results from an initial GWAS are taken forward into additional samples), we extracted the sample sizes at each stage and the statistical threshold for moving SNPs forward into the next stage. We then calculated the sample size for which a one-stage design would have equivalent power as the actual study, and plotted this “effective” sample size against the number of loci that reached genome-wide significance (P<5×10−8 (70, 79)). As had been seen previously, the number of loci reaching genome-wide significance increases with sample size (Figure 2), and, where there is a broad range of sample sizes, the increase appears to be approximately linear. Furthermore, if we omit the largest study and use
