Robert, I take your point on birth control, which I hadn’t thought about in an absolute sense: i.e., choosing to forgo reproduction completely as a lifestyle choice. Rather I was thinking of those who want children but consciously limit the number of offspring. It would be interesting to find reliable statistics correlating reproduction rates with political orientation; I thought I read a while back that self-identifying liberals had fewer children, and of course, abortion is practiced more among liberals than conservatives (at least I assume so).
However, I still think there are solid reasons to assume that modern, First World (if we can still use that phrase), middle-class individuals rationally will choose to have fewer children, in part as a way to ensure the long-term success of both parents and offspring. If so, then the number of K-selectors will not go down over time, but indeed may go up in general, and particularly in periods of economic stress, war, and general uncertainty. In part, I would think that statistically, you have to take the entire set of reproducing families, and over the past several decades, that seems to affirm a continuation of K behavior. Again, this is different from ensuring the survival of families and the individual, which I think is explained equally by both r and K strategies.