A cabdriver in Tehran helped Ramtin Arablouei crystallize the idea.

“People in the West, they don’t remember anything,” the driver had told him, diagnosing the cultural divide between Iran and the United States. “And people in the East don’t forget anything.”

That inspired his mission when he and fellow NPR producer Rund Abdelfatah launched their history podcast, “Throughline,” in 2019: to help Americans remember. Their show explored the Sunni-Shia divide, the ruthless beginnings of the banana industry, the invention of race — the kinds of compelling but knotty stories that have fueled a booming market for podcasting among younger listeners.

And after two years, their bosses decided to take “Throughline” to the larger audience of radio.

“We have a really young audience, and that was part of our goal,” Arablouei said. “But then we knew that the radio audience skews older and Whiter, and we thought this is important for them to hear, too. These are stories that are really worthwhile no matter where you fit in the demographics of the U.S.”

NPR — which this week celebrates the 50th anniversary of its first original radio broadcast — has lately struggled with the need to bolster a listenership that is rapidly aging. Increasingly, it has branched out into digital media, where younger and more diverse listeners already are, particularly podcasts. Now, programs that have cultivated huge followings in the podcast world are making their way to radio, and to a vastly different group of listeners.

NPR’s podcast-listening audience far more closely mirrors the country’s racial demographics than does its traditional radio audience, according to data compiled by ratings firm Nielsen for NPR and shared with The Washington Post.

People of color make up 42 percent of NPR podcast listenership, compared with 21 percent of its radio audience. And although the majority of NPR radio listeners are older than 44, the majority of its podcast listeners are between the ages of 18 and 44.

Podcasting “helps us reach our number one goal,” NPR chief executive John Lansing said, “and that is to reach a younger, more diverse audience, and to expand NPR into parts of the American community that [have] otherwise not really found maybe so much resonance with NPR.”

Part of the reason the podcasting audience is more racially diverse may be inherent to the format itself, which generally attracts a younger audience, a demographic that is more diverse.

Podcasts also generate NPR’s largest chunk of corporate sponsorship money, one of the public radio giant’s most important sources of revenue. The amount that NPR’s podcasts have made through this avenue has tripled in the past five years, Lansing said.

But radio remains paramount for NPR, which relies even more heavily on the fees it receives from affiliate stations nationwide. These local “member” stations get money through various means, such as pledge drives, sponsors and the federally funded Corporation for Public Broadcasting. The local stations, in turn, pay NPR to broadcast its programs, including flagship shows “Morning Edition” and “All Things Considered,” which Lansing called “the foundation of NPR across the country.”

And twice as many people listen to NPR content on the radio — an estimated 26.1 million people weekly — than to its 47 podcasts put together. Those two audiences have little overlap, according to internal figures.

“We’ve got this very core audience that is very loyal to NPR,” said Yolanda Sangweni, NPR senior director of programming. NPR wants to “continue cultivating a deeper sort of loyalty and serving them with our content, but also letting them see that there’s this new, younger audience that we can also bring into the fold.”

Some NPR radio shows have also adapted to podcasting, such as “Up First,” an abbreviated take on “Morning Edition.” But podcasting has turned into an incubator of sorts for new radio shows, with several now making their way to local airwaves. “Throughline” debuted on radio in January and will be on 81 stations by June, and culture and news podcast “It’s Been a Minute With Sam Sanders” is now carried by 409 stations.

Among the next will be “Code Switch,” which Apple Podcasts named its show of the year in 2020. “Code Switch” tackles race, identity and culture by putting people of color at the center of the show, although White listeners still make up a slight majority of its audience.

“The White folks who are listening in are eavesdropping. They’re not the people who are at the center of the conversation, which I think is a more subtle distinction than people often realize,” co-host Gene Demby said.

Starting out as a podcast offers show creators a chance to explore and experiment while also building a following — which can help when the subject matter is inherently challenging. In the case of “Code Switch,” the hosts and producers found the space to “be as authentic as they needed to be . . . without having to wonder, ‘Oh, is this going to affect listenership in broadcast?’ ” Sangweni said. “So now, by the time they go to broadcast, they’re very clear about their point of view, and they want to spread that out to more people that may not necessarily be downloading podcasts.”

The demographic data compiled by Nielsen found that 17.8 percent of NPR podcast listeners are Hispanic, 15.5 percent are Black and 6.2 percent are Asian. By comparison, NPR’s radio listeners are 10 percent Hispanic, 7 percent Black and 5.1 percent Asian.

Some of NPR’s podcasts with the most racially diverse listening audiences have nothing explicitly to do with race or identity. The business show “How I Built This” draws an audience that is just over 19 percent Black and more than 18 percent Hispanic.

NPR bosses insist that their podcasts keep their same old sensibility when they jump to radio. Still, “Code Switch” co-host Shereen Marisol Meraji has some anxiety about the response from the radio audience when stations begin airing the show this summer. Their current listeners have to actively choose to tune in, she notes, adding: “They want to hear what we have to say. They want to learn about race and identity and culture.” But that won’t be the case for all radio listeners. Will they bristle at how “Code Switch” handles topics ranging from reparations to the origins of “Karens.”

On the flip side, Demby notes, is the opportunity to find more listeners, including people of color who “fortuitously stumble upon us.” That, in turn, could expand the NPR radio audience.

“There is a chance of being pleasantly surprised by people,” he said, “and people being pleasantly surprised by us.”

The podcast-to-radio transition has also helped diversify the ranks of on-air hosts.

“We were producers, had never been on air, we were not the traditional-looking hosts — and by that I mean we were not White, and we were younger,” said “Throughline’s” Abdelfatah, who is of Middle Eastern descent like co-host Arablouei. “It’s really powerful and important for people to hear names like ours on the radio, and to see faces like ours.”

The feedback thus far has been reassuring. Teachers and other new listeners have thanked them for creating compelling historical pieces for the radio.

Abdelfatah considers the success of the show “not just for us, I hope. I think it’s proof that people do want different perspectives on air, and to see a different way of looking at the world.”