Opportunity for selection in the parish of Tuna, Sweden.

This article is part of a series of studies on the opportunity for selection in Swedish populations. The study concerns women who, with some exceptions, were born during the first half of the 19th century. A modified form of Crow's index has been used to estimate the upper limit of natural selection. The average index for the period 1805-1850 was I = 1.136, which value falls within the limits of what has been found for the other Swedish populations that have been studied.