The beauty of cards is that the universe is known; there are fifty-two cards in a deck, and only fifty-two. Life insurance is a bit different: since new people are always being added to the universe, actuaries rely on samplings. They aren’t perfect, but they work, because the sample of people is very large and mortality rates change only very slowly. But in markets, we are never sure that the sample is complete. The universe of all trades looked one way throughout the 1920s and another way after the Great Depression. The pattern changed again during the inflationary 1970s, yet again in the
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