Economists often distinguish between cyclical trends and secular trends — which is to say, between short-term fluctuations and long-term changes in the basic structure of the economy. No decade points to the difference quite like the 1930s: cyclically, the worst decade of the 20th century, and yet, secularly, one of the best.

It would clearly be nice if we could take some comfort from this bit of history. If anything, though, the lesson of the 1930s may be the opposite one. The most worrisome aspect about our current slump is that it combines obvious short-term problems — from the financial crisis — with less obvious long-term problems. Those long-term problems include a decade-long slowdown in new-business formation, the stagnation of educational gains and the rapid growth of industries with mixed blessings, including finance and health care.

Together, these problems raise the possibility that the United States is not merely suffering through a normal, if severe, downturn. Instead, it may have entered a phase in which high unemployment is the norm…

Perhaps the most important reason, beyond the financial crisis, is the overall skill level of the work force. The United States is the only rich country in the world that has not substantially increased the share of young adults with the equivalent of a bachelor’s degree over the past three decades. Some less technical measures of human capital, like the percentage of children living with two parents, have deteriorated. The country has also chosen not to welcome many scientists and entrepreneurs who would like to move here.