Policymakers often promote higher fertility as a way to offset the impact of population ageing without increasing immigration. This column uses OECD and United Nations projections to argue, however, that higher fertility would depress GDP per capita growth for roughly 50 years. Mobilising women and older workers could avert this slowdown, but more births would likely lower force participation among these groups. Conversely, increased labour immigration can coexist with higher fertility. Simple