The authors continue to fixate on the concerns and challenges that are supposedly created by those selfish non-procreators. Whose going to replace the workforce? What about all those elderly entitlements? (Of course, he seems oblivious to the fact that adults without children–particularly DINKs–are likely to have more resources to work with and be less of a social burden). The authors are not concerned about the overall continued population growth in the world, but about the United States. So much of the challenges that he points to–only exist because of a self-interested and one might say selfish approach to looking at human population. These are artificial threats created by an artificial barrier called nation. Here, the authors are playing upon a xenophobic bias (his own and the readers) to ignore the larger picture and just frame the US in a state of crisis (making note that we could go the way of Europe or Japan who also face population declines) that is in part, caused by the childfree selfish people.