Probably the best result would be a soft leveling off rather than abrupt stoppage in reproduction anywhere. Interestingly, some historians claim the Black Plague in Britain/England caused a disruption which later on cascaded in such way to allow the the transition from feudalism to more capital intensive economics (same wealth distributed among fewer heirs).

Some of the worst offenders, which are generally companies and governments, are led by educated, motivated kits in the developed world.