Will the current decade turn out to be like the 1920s, 1970s, or 1990s? We are still assigning subjective probabilities of 60% to the Roaring 2020s (like the 1920s), 20% to a second peak in inflation (as occurred during the 1970s), and 20% to a bout of irrational exuberance (like the late 1990s).