Source of population data
In b23dafba, we introduced a GPKG file with a world-map (country-level borders) and country-level population size predicted for 2020 (as per the commit message). In 42eba020, we changed the plan accordingly to use population data from this file, instead of the previous approach of downloading data from UNs WorldPop database, which also gives estimates for 2020, separated by sex.
I'm not sure of the reason for this switch and the source of the GPKG has not been annotated. Furthermore, the file name includes "2013", which makes me wonder whether this is really an estimate for 2020.