The remaining level of unemployment that occurs even when the economy is healthy is called the:

1. Even a strong economy never reaches zero unemployment. 2. Some unemployment persists in good times as well as bad. 3. Economists have a term for that remaining level. 4. They call it the natural rate of unemployment. _Source: OpenStax Principles of Macroeconomics for AP Courses 2e (CC BY 4.0), Ch 7 'Unemployment'_