Overseas research suggests that the mentally disabled account for about 2 % of the population, and 80 % or more of them are only mildly disabled, that is, with the mental age of a seven-11-year-old child.
依據國外研究推估，智能障礙者約佔總人口的 2％，其中 80％以上是輕度障礙，心智年齡相當於 7 至 11 歲兒童。