The SNPs for which one variant is statistically more common in individuals belonging to one phenotypic group are then reported as being associated with the phenotype. However, most complex common diseases involve small population-level contributions from multiple genomic loci. To detect such small effects as genome-wide significant, traditional GWAS rely on increased sample size e.g. to detect an effect which accounts for 0.1% of total variance, traditional GWAS needs to sample almost 30,000 individuals.