Since C9orf72 expansions cause both ALS and FTD, we modeled both diseases separately, providing for C9orf72-ALS an expected number of people affected over two times higher than previous estimates (Supplementary Table 10: 1.8 per 100,000 versus 0.5–1.2 in 100,000 (refs. 4,31)) and for C9orf72-FTD 6.5 per 100,000 (Supplementary Table 11) within the wide reported range32,33. The gene discussed is C9orf72; the disease is frontotemporal dementia.