In the past two decades, the median age of workers in the United States has risen from 40.3 years to 42.4. It might not sound like a big change, but it’s having a big effect. This aging workforce is one reason the Bureau of Labor Statistics estimates that annual U.S. employment growth will slow to just 0.4 percent over the next decade, less than a third of the 1.3 percent annual growth recorded between 2013 and 2023.