There is an ongoing debate about the value of cities hosting the Olympic Games. And that’s because this is usually how it works: You, the host, spend a lot of money (Tokyo 2021 was over $25 billion), it feels really good during the games while the world is watching you on TV, and then everyone leaves and you have a big bill to pay.

As I understand it, this has generally been the case for almost all of the games. One rare exception is Los Angeles in 1984, which supposedly managed to make over $230 million from hosting. In pretty much every other case, the rough value was, at least in theory, things like exposure, ego, and hopefully a bunch of assets that will remain useful to other people once the games are done.

But as I have argued a few times before, perhaps the most important hard-to-quantify benefit is this: Hosting the Olympics creates an immutable city-building deadline. Because, what could be worse than not being ready when your global guests show up?

A perfect example of this is what Paris is now trying to do with the Seine ahead of the 2024 Olympics. The goal is to clean up the Seine so that it’s actually safe enough for the athletes to compete in it. That would obviously be really cool for the games, but it would also be a wonderful legacy for Paris.

Would Paris still be doing this if it weren’t hosting the games? Perhaps. Paris has a habit of doing some obviously good things. But I bet it wouldn’t be moving nearly as quickly.