The declining U.S. birth rate, and the broader demographic shifts it contributes towards, have become a growing concern for policymakers and economists alike. Economic and demographic experts told Newsweek that the trend is one that threatens to destabilize not only the U.S. economy—potentially resulting in several percentage points being knocked off America's annual GDP growth—but global markets as well. "I think it's the single most important issue facing economies across the world, and by some distance," said James Pomeroy, a global economist at HSBC. As is the case with almost every country on earth, U.S. birth rates have been trending...