You know what would be even more efficient.... Fewer people...
Literally the same argument that Hitler made:
> The Nazi Generalplan Ost policy ('Master Plan for the East') was based on its tenets. It stipulated that Germany required a Lebensraum necessary for its survival and that most of the indigenous populations of Central and Eastern Europe would have to be removed permanently (either through mass deportation to Siberia, extermination, or enslavement) including Polish, Ukrainian, Russian, Czech and other Slavic nations considered non-Aryan.
Instead we should be trying to grow populations as we're headed for a demographic collapse requiring extremely high taxation of the young to care for the old. It's a slow moving disaster.