Because everything is good news for Republicans, right? Here's a map, courtesy of Daily Kos, showing when population peaked by county in the United States. The palest yellow counties are at essentially peak population now, with successively darker counties having peaked earlier, the violet ones peaked in the 19th century:
This does not bode well for the chances for Republicans to reverse their party's decline. If it keeps up, they can only look forward to representing less and less of the population.