One Economic Sickness, Five Diagnoses. N. Gregory Mankiw, June 17, 2016, Opinion. “Economists, like physicians, sometimes confront a patient with an obvious problem but no obvious diagnosis. That is precisely the situation we face right now. Let’s start with the problem. There is no simple way to gauge an economy’s health. But if you had to choose just one statistic, it would be gross domestic product. Real G.D.P. measures the total income produced within an economy, adjusted for the overall level of prices.Link