The first step in treating a severe illness is making the correct diagnosis. Since passing the stimulus package in early 2009, President Obama and his economics team have groped for a good explanation of why the economy remains stuck in a long-term slump, and in particular, why job growth has remained so slow. The answers have variously been high health care costs, fiscal profligacy by the Bush administration, recklessness on Wall Street, excess dependence on foreign oil, and a poor education system.