American decline is a popular narrative these days. It's a central feature of Donald Trump's presidential campaign — you can't "make America great again" unless America isn't so great right now. Although Trump often seems disconnected from reality, on this issue he has a point. The United States is in decline. Fortunately, the slide isn't severe, and there's probably time to arrest its progress or prevent it from accelerating.
When we say a nation is in decline that can mean several things. Historically, it meant a fall in living standards and the level of economic development. When the Roman Empire declined, the population of Rome shrank, roads crumbled and the empire's ships disappeared from the ocean. Eventually the European continent fell back into poverty and violence among regional and city-state powers. The same thing happened to China after the fall of the Han Dynasty, and again after the fall of the Qing Dynasty.
Nothing of the kind threatens the U.S. today. Yet it is true that the economic well-being of the average American — defined as median household income — has fallen since the turn of the century: