  We consider the problem of probabilistic projection of the total fertility
rate (TFR) for subnational regions. We seek a method that is consistent with
the UN's recently adopted Bayesian method for probabilistic TFR projections for
all countries, and works well for all countries. We assess various possible
methods using subnational TFR data for 47 countries. We find that the method
that performs best in terms of out-of-sample predictive performance and also in
terms of reproducing the within-country correlation in TFR is a method that
scales the national trajectory by a region-specific scale factor that is
allowed to vary slowly over time. This supports the hypothesis of Watkins
(1990, 1991) that within-country TFR converges over time in response to
country-specific factors, and extends the Watkins hypothesis to the last 50
years and to a much wider range of countries around the world.
