“In science fiction, it’s always about now,” Margaret Atwood told the Guardian in 2018. “What else could it be about?”

I recently reread her novel “The Handmaid’s Tale” for a little light relief while reporting an article about falling birthrates. In the book — which, for the record, I have loved for decades — an ecological disaster has rendered much of the population infertile. Christian extremists overthrow the U.S. government and institute an elaborate system of reproductive slavery: Fertile women are sent to live with high-ranking officials who rape and impregnate them, then take the children to raise as their own.

“A Handmaid’s Tale” belongs to the genre of speculative fiction about societies grappling with the aftermath of a precipitous fall in birthrates. The film “Children of Men,” adapted from a novel by P.D. James, is another example of the genre. The plots usually assume it would take a mysterious disaster to cause people to stop having children.

In real life, shrinking birthrates do not unfold like a Hollywood plot. The causes are multifaceted and complex. But a growing body of research suggests that plummeting birthrates are partly caused by economic growth itself, which has the unintended side effect of making parenthood more difficult and expensive.

People in rich countries have fewer children

There are many factors that can contribute to lower fertility rates. China and India, for example, both had decades-long government programs designed to lower their birthrates. And experts have suggested that many other aspects of modern life — birth control, shifting marital patterns, increased career and education opportunities for women, and perhaps even smartphones — could also play a role.

But the statistics are very clear. As economies get richer, children get rarer. Today, nearly all developed countries have fertility rates between 1.2 and 1.8 births per woman, significantly below the “replacement level” of 2.1 that allows populations to remain stable over time.