2025-07-01
9 分钟NPR Here are two seemingly contradictory truths about the people of planet Earth.
The first is that over the past century, the world's population has exploded,
going from around 2 billion people to 8 billion people today.
truth number two is even as the Earth's population has boomed the average fertility rate has declined and
if things keep going that way a few decades from now the world's population will actually start to shrink and Just as the world's population spiked in recent centuries It could also crash and our guests today say that we're living near the very edge of this crash This is The Indicator from Planet Money.
I'm Adrian Ma.
Today on the show, our guests are economists Dean Spears and Mike Geruso.
They've co-authored a forthcoming book called After the Spike,
Population, Progress, and the Case for People.
And when we come back, they'll explain why, population-wise,
the human party will soon peak, and why that's a problem.
For economists who study population growth and decline,
the fertility rate is a very important metric.
The fertility rate is the average number of children a woman has in a lifetime.
And here, two is kind of the magic number.
That's what demographers call the replacement rate.
And when the global fertility rate falls below two for long enough,
that leads over time to something called depopulation.
Depopulation is the name for what happens when birth rates are low enough that the population shrinks decade by decade and generation by generation.
This is Dean Spears, an economist at the University of Texas at Austin.