Well North Korea still has around 2 fertility rate lol. Of course this is more due that poorer countries in general have higher birth rates.
Age pyramid of North Korea as of 2016:
Age Pyramid of South Korea as of 2016:
It's odd how so many of the large Asian countries have this impending demographic issue. China, Japan, South Korea and Thailand all have this problem. North Korea, Indonesia and the Phillipines do not. Given how significant an impact this can have on the success of nations I think we'll see a bit of a shift (slow and gradual as it may be) of power toward those with more sustainable population levels and away from those that are going to collectively grow old while seeing a population decline.