Improving estimates of all contributors to heritability will facilitate determination of the proportion of genetic variance that has been explained. Despite imprecision in current estimates, it may still be possible to know that ‘all the heritability’ has been explained by predicting phenotypes in a new set of individuals from trait-associated markers, and correlating the predicted phenotypes with the actual values. If the markers truly explain all the additive genetic variance, the squared correlation between predicted and actual phenotype will be equal to the heritability40. Population-based heritability estimates thus provide a valuable metric for completeness of available genetic risk information, but individualized disease prevention and treatment will ultimately require identifying the variants accounting for risk in a given individual rather than on a population basis.
