The list only includes single, widowed or divorced women, so in that regard the list has been created from a bit more filtering than just age. EDIT: to your po

The list only includes single, widowed or divorced women, so in that regard the list has been created from a bit more filtering than just age. EDIT: to your point however, being married would not preclude a woman from being "breed ready" as we understand the phrase. So clearly there is some missing context needed to really understand what that column represents.