Robert Fenge and Beatrice Scheubel write that they provide,
an empirical confirmation of the negative relationship between statutory old-age insurance or more broadly statutory social insurance and fertility. The effect amounts to a total reduction of approximately 1.7 marital births per 1000 between 1895 and 1907… [the] impact of pension insurance is comparable to the impact of an increase in urbanisation by 10-20%.
Pointer from Brian Blackstone
Off hand, it would seem to me that any form of capital accumulation by the elderly could have this effect. Private pensions certainly, and perhaps even private savings for retirement. But it might be argued that there are huge negative externalities in public pensions, in that they allow you to benefit from my having children.
Alan Macfarlane in his ‘The Invention of the Modern World’ had this observation regarding the changes in demographics.
“Putting it simply, in an embedded peasant economy, when the unit of production and consumption is the family household, it is sensible to have as large a family as possible, to work the land and to protect against risk in sickness and old age. To increase reproduction is to increase production. Yet as Jack Caldwell and others have shown, when the individual becomes integrated into the market, when wealth flows down the generations, when the cost of education and leaving for an independent economic existence on an open market occurs, children become a burden rather than an asset.23 In other words, capitalistic relations combined with individualism knocks away the basis of high fertility, and if this is combined with a political and legal security so that one does not have to protect oneself with a layer of cousin, the sensible strategy is to have a few children and to educate them well.
“A low-pressure demography means that a society avoids the situation where extra resources are automatically absorbed by population expansion. As Malthus argued, the only force strong enough to stand against the biological desire to mate and have children, was the even stronger social desire to live comfortably and avoid poverty. This is exactly what seems to have happened in England from at least the late medieval period.”
http://fortnightlyreview.co.uk/2012/07/invention-8/
It appears to me that the 20th century with the rise of the Welfare state was a transition period. The decline in mortality pressures outpaced the adjustment in the birth rate but as we see, fertility has become the driving factor with birth rates rather than mortality. Unfortunately, the move toward public welfare was based on the false premise that the decline in mortality creating an increasing workforce wouldn’t be counteracted by an adjustment in fertility with not only abortion and birth control, but also later marriage and births.