I suspect that North Korea is probably in the same 10/40 window. Christians in North korea have a very hard time. Getting scriptures into North Korea is extremely difficult and the povety in quite a lot of that country means that most rural Christians in Korea do not have any access to any modern telecommuniations at all. Tourists to North Korea are under survailance 24 hours a day. It is very hard for Christians to work for the gospel in that land at all. A well know underground organisation, (whose name I will not mention on the internet), publishes a watch list and North Korea is pretty much one of the most persecuted countries for Christians anywhere in the world.