Even though the U.S. is one of the world's leading exporters, few companies actually sell abroad. One reason may be that exporting requires a company to be highly productive.

Businesses have found that it can pay off to engage in social stewardship, such as donating to charity, protecting the environment and nurturing a diverse and safe workplace.

Cities initially more specialized in older technologies may have had more difficulty adapting to newer technologies because skills in initially dominant industries were not useful to new industries.

According to economists, in the 1980s and 1990s, immigration of low-skilled workers may have increased the labor supply of highly skilled women, and immigration of highly skilled workers may have increased the rate of innovation in the United States.

Better-educated people appear to be in better health than less-educated people. But does more education cause better health, or are there other factors at play – such as income and access to information?