David Leonhardt: Trend toward inequality means America will struggle after the coronavirus

America’s economy has almost doubled in size over the past four decades, but broad measures of the nation’s economic health conceal the unequal distribution of gains. A small portion of the population has pocketed most of the new wealth, and the coronavirus pandemic is laying bare the consequences.Consider first the most commonly quoted measure of the nation’s success — gross domestic product, which measures a country’s total output — in the first chart below.