[Balgair]

I was going to say that the math was off by 2, but nope, you're right. Fertility rate is based on each woman, not on a couple.

Even if they kept the 0.81 rate that they are on, then you'd get:

Gen1: 100 people: 50 men + 50 women; 50 women have 40 babies (40.5, but lest round to just 40)

Gen2: 40 people: 20 men + 20 women; 20 women have 16 babies

Gen3: 16 people

Given that the current average age of a woman at the time of her first birth in SK is 33 years old (!?!?!), you'd expect the 100 people of SK to be just 16 people somewhere near 2090. Meaning that it's current population of ~52M goes to ~8M in ~70 years. An 84% reduction in 66 years, or 1.28% per year.

And it looks only like it'll get worse for them.

I can't think of any war or plague or natural disaster or famine that has ever done such a number to a population of that size over that long of a time. Granted, that hasn't happened yet.

Still, whatever the hell is happening to them is something to be avoided like a war or a famine or a plague.