A New measure of fertility replacement level in the presence of positive net immigration

In most more developed countries, the total fertility rate (TFR) is below 2.1 and net immigration is positive. This paper proposes and calculates for 22 populations for 2011–15 a ‘Current Migration Replacement TFR’ which in combination with the mortality and absolute net migration for that period generates a stationary population equal in size to the mid-period population. The results show the Current Migration Replacement TFR ranges widely from 0.60 for Singapore to 2.05 for Slovakia. That the Current Migration Replacement TFR is below the 2011–15 TFR in 14 of the 22 countries shows that, when considered in combination with current migration and mortality, in most of the countries the current ‘below 2.1’ TFR is coherent with population increase, not population decline, over the long run. For New Zealand, Australia, Norway, Sweden and the UK continued current fertility in combination with constant mortality and constant absolute net migration is coherent with more than doubling of the current population size. The value of this measure for illustrating the interconnected population size implications of sub-replacement fertility and immigration, for sub-categorisation of ‘post-transitional’ populations by population growth prospects, and for guiding population policy is discussed.