The total fertility rate is below the replacement level – the number of children needed to keep the total population constant – in 32 out of 34 OECD countries for 2010-15. The exceptions to this are Israel with a replacement rate of 2.9 and Mexico at 2.2. However in two-thirds of OECD countries there has been a moderate increase in fertility rates over the last decade. Fertility rates have a profound implication for pension systems because they, along with life expectancy, are the drivers of population ageing.