Nobody Is Going to Conventions. Convention Centers Are Growing Anyway.

“There’s various ways they could do it,” he said. “It’s not straightforward.”

Even in the best of times, convention centers are loss leaders, said Mr. Sanders, the Texas professor. But the convention business has faced severe boom-bust cycles over the past two decades, with steep downturns after the terrorist attacks of 2001, the financial meltdown of 2008 and now the pandemic.

On Tuesday, the organizer of BookExpo, the country’s largest publishing trade show, canceled the 2021 event and said it would rethink its format for the future, suggesting that it would include both “in-person and virtual offerings.” In recent years, BookExpo was held at the Jacob K. Javits Convention Center in Manhattan.

If enough events go away, local taxpayers could end up paying back debt that centers took on to expand, Mr. Sanders said. “You’ve made a very large bet in an environment of enormous risk and uncertainty,” he said. “And once you place it, you can’t undo it.”

And that drives cities to keep building. Consider the chain reaction caused when the National FFA Organization sought greener pastures.

The group, once known as the Future Farmers of America, is prized for the tens of thousands of conscientious teenagers it brings to town. After 1998, it spurned Kansas City, Mo., its host city for 70 years, despite offers of cash, a free building and other incentives. The FFA was growing fast, and Kansas City wasn’t keeping up: Event space was tight, and local hotels sold out, forcing some teenagers to sleep 60 miles away in Topeka, Kan.

The group decamped to Louisville, Ky., where the fairgrounds were expansive. But soon the hotel crunch was even worse: Some attendees were booking rooms 90 miles away. That was when Indianapolis pounced, landing the 2006 convention with the promise of more hotel rooms and donations from local businesses to hold down registration fees.

But no sooner did Indianapolis bag the future farmers than it lost the Performance Racing Industry Trade Show, which took its business to Orlando, Fla. — where there was more space.