This is certainly part of the cause for lower birth rates, but I think the prevalence of state-funded old age welfare is a huge factor too.

In the past, aging parents relied on their children to help take care of them. In an age of the mass forced transfer of wealth from the young to the old in the form of Social Security and similar programs in other countries, the past few generations have enjoyed the financial benefits of having children without paying the costs of having to actually raise them. While this certainly doesn’t discourage everyone, the effects of incentives are seen on the margin. We shouldn’t be surprised that government subsidies covering for the lack of support from children leads to less children being born.

Allowing the old to live off of other people’s children rather than needing to either have their own savings, their own children, or both, is one of the greatest mistakes of the 20th century. I’m hopeful that it’s an idea that dies with fiat currency.