Should be mentioned that Minnesota, the Dakotas, and Iowa are always at the top of the list in terms of educational tests and have the lowest rates of divorce, FWIW.
The real reason South Dakota has such low unemployment is that people simply leave the state when they lose work, and virtually nobody moves TO North Dakota. The state’s population peaked in 1930. They also have a hard time keeping their young people, a source of much hand-wringing in the state, which is graying rapidly.