The persistence of low fertility rate is one of the many factors inhibiting the stability of public pension systems in developed world. From the 20th century onwards fertility rates have plummeted in all countries that belong to high-income group. The causes of this systematic drop in average fertility rates could be attributed to income affects of higher education and human capital as well es to greater perticipation of women in the labor market. The fertility rate used to stand above average in countries where the dominance of hierarchical religion has been present. Catholic countries such as Ireland, Portugal and Spain were known for extensive influence of religion on fertility decisions regarding the number of children. Thanks to greater use of contraceptive means, the fertility rates in those countries have stadely converged to the level of fertility in Protestant countries. In recent years, the fertility rate in Catholic countries has been ranked at the bottom in high-income country group.
In concidering the features behind lower fertility rate, the influence of taxation of labor supply has been neglected. In Catholic countries, the rate of female participation in the labor market was significantly lower than male labor perticipation rate. The spread of the welfare state in developed countries in the 20th century led to significant spikes in marginal tax rates on labor supply. For instance, 45 percent marginal tax rate implies that from each additional dollar earned, 45 cents go directly to the governement. The implication is that tax burden of labor supply nearing predatory levels does not encourage men and women to spend more time in the labor market. Consequently, the level of earnings decreases in the course of life cycle, further reducing the parental willingness to increase family size.
It is difficult to reverse the tax burden of labor earnings since the continuous growth of the welfare state amassed significant financial labilities of the government. To boost fertillity rate, it is essential to expand incentives to participate in the labor market, postpone labor market withdrawal and increase the family size. Without a prudent reduction of marginal tax rates and effective tax burden of labor supply, the Western world will experience decades of stagnating fertility rates whose negative impact on the stability of public finance could be difficult to reverse.