In interviews with me this week, the mayors of several of those big cities told me that it will take much longer than a few weeks to restart their economy—and that even when economic activity resumes, the process will be gradual and halting.

In other words, they counsel, Americans shouldn’t expect the equivalent of a V-E or V-J Day when the virus is vanquished and life goes back to normal, as if turning on a light switch. Instead, the mayors envision something more like a dimmer switch that gradually grows brighter.

Read: How the coronavirus became an American catastrophe

Los Angeles Mayor Eric Garcetti told me that he believes the city’s shelter-in-place order will need to remain in force at least through mid-May, two months after he issued it. “Easily, the worst thing you can do is kind of crush people’s hopes by setting up early expectations [of lifting restrictions], when we are going to be in this for a long haul,” he said. “The best thing” people can do is understand that the outbreak “won’t come in one fell swoop and one wave—and prepare for that.” That means that any easing of restrictions on economic and social activity later this year will be gradual, Garcetti said.

Or as Dallas Mayor Eric Johnson put it: “No one can be sure, but I have a hard time imagining that there will be a day when everything goes back to normal: just one day everyone is sheltering in place, businesses are closed; the next day, it’s all over.” His city is operating under strict shelter-at-home regulations. “What I can more easily envision is a gradual unwinding of the most restrictive emergency orders or regulations and a ratcheting back to normal.”

And even that gradual process, Johnson told me, is unlikely to start as soon as the president hopes.

“I’m not certain by any stretch that we will be out of the woods by April 30,” he said. “I think that’s for public-health experts to prognosticate about, and it’s going to be up to the virus to determine when we are out of that.”

Two intersecting trends explain why these large metropolitan centers are positioned to play such a pivotal role in the pace and extent of any economic recovery from the outbreak.

One is long term: As the nation transitions deeper into an information-based economy, skilled workers, venture-capital investment, scientific research, and new-business formation are all concentrating more heavily in the nation’s biggest urban areas. Those regions include many cities, from Seattle to New York, that appeared to face terminal decline during the final decades of the 20th century. As Muro and his colleagues have repeatedly documented, those areas now account for a growing share of the nation’s total economic output and jobs.

“Sure, there are important [economic] clusters everywhere,” Muro said. “But ultimately, if we’ve learned one thing in this decade,” it’s that the American economy is now powered by “the intense concentration of advanced economic activity” in the biggest cities, “and the multiplying effect of that concentration” on productivity.