Gross domestic product in the U.K. contracted by a staggering 9.9 percent in 2020, the biggest slump since the invention of the measure itself in the 1930s. Economic historians who have tried to retrospectively calculate GDP for the years prior to the 1930s reckon that the 2020 economic collapse may be narrowly worse than the 9.7 percent fall of 1921, as the world was battered by the influenza pandemic. To find a worse recession, British economists say, you have to go back to the Great Frost of 1709, when a prolonged winter, so cold that Venice’s lagoons froze over, crippled European nations.