It's a very important observation in finance that returns on a lot of speculative assets have fat-taileddistributions.
在金融界中，这是一种重要的观测方法，许多投机性资产的收益，都是服从长尾分布的。
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This is because in fat-taileddistributions, the mean is affected by outliers and therefore one needs many years of data to arrive at a stable estimate.