My two posts from yesterday on why supply-siders should get behind a tax reform that includes an expanded child credit drew this response from one of my Social Security gurus:

While I don’t particularly disagree with your general policy recommendations re families/fertility, etc., Stein’s general point re entitlements and fertility seems wrong. It’s true that pre-industrialization a good chunk of people’s retirement savings was investment in the human capital of their children, but that was due to the unavailability of financial capital such as stocks and bonds. Once financial assets became widely available, fertility probably would have fallen regardless of whether Social Security was implemented, simply because people had a more efficient means to save. (After all, one reason people had large families is that not all their kids could be counted on to actually care for their parents.) Put another way, lacking Social Security/Medicare today, it’s more likely that people would increase their saving than their family size. I’m not sure this is necessarily a bias to be fixed so much as simply people acting rationally.

I don’t take Stein to be arguing that government-provided pensions and the taxes they require are the only reason for the decline in fertility, merely that they have contributed to that decline.

Update: Stein writes in:

Clearly Social Security and Medicare are NOT the primary reasons behind the decline in fertility versus the pre-industrial era. The fertility decline is mostly related to rising prosperity and the availability of alternative means of saving for retirement. My child-credit proposal is not intended to offset those effects or return us to pre-industrial levels of fertility. (If it did, my wife would have killed me by now.) It is simply intended to offset the (comparably modest) impact of SS/Medicare.