human trends (fashion and emotion based) create patterns that people can rely on until the trend stops, then their is much thrashing around until new patterns form and you can exploit those until they stop.
not like its a rule of nature, just a rough guide to the averages of the past, until the "now" is sufficiently different to the "then"
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its why governments are so scary in my country at the moment, they consider these rough rules of thumb based on previous trends as gospel.
the invisible hand of the market was never a concept about being a perfect thing that didnt stuff up, it was a concept of the market fixing the stuffup quicker than a central government can, but none of the anti capitalists want to hear that nuance, they want this absurd world that agrees with them and never stuffs up.