The assertion being people who want to have threesomes are less likely to have children? I suppose that could be the case, however I am fairly unconvinced that

The assertion being people who want to have threesomes are less likely to have children? I suppose that could be the case, however I am fairly unconvinced that this has any real affect on the population in comparison to the cost of having a child coupled with the rise of understanding the costs involved with having a child.