There are a lot of Southern states on this list that are seeing a high percentage of people moving both out and in. South Carolina, like many others, has seen a flood of people move to the state in recent years, but a lot of people are also leaving. Poverty rates are still pretty high in rural areas, and good-paying jobs tend to be located in more urban areas, which is a growing problem everywhere.
The state has seen a lot of people move in ever since Covid, but before that, there were some large dips, so its average population hasn't changed as drastically as some others.