In South Korea, many people and doctors didn’t want to stop checking for thyroid cancer so often, even when it might not be needed—some even said it was a right everyone should have, suggesting that money and institutions might be pushing unnecessary tests.

Doctors in South Korea told people to stop getting unnecessary thyroid tests, and suddenly fewer people had surgery — showing that when doctors change their minds, overtesting can drop, which supports the idea that doctors and hospitals were pushing too much screening before.