Answer:
There are several regions in the United States that have been losing population and will lose weight in the electoral college as a result.
The two regions that have lost the most population in recent decades are Appalachia, and the Rust Belt.
In Appalachia, specially the state of West Virginia has been affected by population decline, due to poor economic conditions. The population of West Virginia fell by -0.3% in the last decade.
In the Rust Belt, the state of Illinois has been the most affected. The population of the state fell by -1.2% in the last decade.