You are in a city where tax authority reports that average income is $50,000, but you do not know what the variance of income is. You want to find the variance so you randomly sample 100 people and ask them what their income is. Let I1 be the income of the first randomly sampled person, and I100 the income of the one hundredth randomly chosen person. Your friend suggests the following estimator of variance of income in the city:

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