U.S. population growth fell to an 80-year low last year amid declining birth rates, a new Census report shows. But it’s also telling that some states are booming while others are suffering a European-style sclerosis of population loss and slow economic growth.

One side effect of a strengthening national economy has been a widening disparity in state growth rates. The eight fastest-growing states by population last year were located in the West or South (Nevada, Idaho, Utah, Arizona, Florida, Washington, Colorado and Texas).

...