Let's start with a small number that has big consequences, the total fertility rate.

It measures how many babies on average each woman will have over her lifetime.

And for a population to remain stable, flat, no growth, no decline, women on average have to have 2.1 kids.

So you need to replace yourself, you need to replace a partner,

and you need a little extra for mortality. That's Philip Levine. He studies population trends at Wellesley

College, and he says this number has been falling in high-income countries, including the U.S.

We're at 1.6, which we're worried about at 1.6. South Korea is at 0.7.

There's just, relatively speaking, no children being born in South Korea.

To understand what a total fertility rate of 0.7 means for South Korea, you just have to

project it forward across a lifetime.

If you take 100 young people today, when they get to be the age of typical grandparents,

those 100 people will have 12 grandchildren.

12 grandchildren for every 100 South Korean grandparents.

Of course, this is unfolding more slowly in the U.S. than in South Korea,

but if it continues, it could remake society

in all kinds of ways. Consider this. The birth rate is falling fast in the U.S., and it's

driving a new political debate about what, if anything, can be done about it.

From NPR, I'm Ari Shapiro.

It's consider this from NPR.

America's falling birth rate has become a political issue, one that's made it all the way to the White House.

I'll be known as the fertilization president that that's okay.

That's not bad.

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