The Heightened Risks of a US Downturn. Martin Feldstein, January 26, 2018, Opinion, "The US economy has experienced nine recessions during the last 50 years. What makes the current situation unusual and more worrying than in the past is the low level of short-term interest rates and the high (and rising) level of federal debt, which will limit policymakers' ability to provide the stimulus needed to counter a recession." Link