Negative Supply Shocks – How often are negative supply shocks, i.e., leftward shifts of the AS curve, which we’ll also discuss next week, associated with recessions? Plot on a quarterly basis since the beginning of the series the real price of oil – measured as the ratio of the nominal price of oil (FRED code: MCOILWTICO) to the U.S. Consumer Price Index (CPIAUCSL). (Make sure to convert index into a price level by dividing by 100. In other words, your transformation should use the equation “a/(b/100)”, where “a” is the price of oil and “b” is the CPI.) Identify recessions that may have been triggered, in part, by an oil price shock.