They sure be takin isolationism to the max when it comes to international relations it seems. (I am in no means certain the actual reasoning, I'm completely ignorant)
Communist countries generally joined the UN no later than the rest of the world. Every ex-communist country in the list is the product of the dissolution of a communist state that had been a UN member.
There are 9 countries tied for 21st: the former members of the USSR and San Marino, all having joined 2 March 1992
There is also a 7 way tie for 30th (the next slot after the 9 coutnries above): the Koreas, the Baltic states, FS Micronesia, and the Marshall Islands all joined 17 September 1991, just about 6 months before the 9 countries above
I'm guessing Taiwan, Kosovo and...?
Bougainville on the other hand will be independent by 2027
What's the lesson? Don't listen to me.
There is also a 7 way tie for 30th (the next slot after the 9 coutnries above): the Koreas, the Baltic states, FS Micronesia, and the Marshall Islands all joined 17 September 1991, just about 6 months before the 9 countries above