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But the fact that so many polls are reporting the exact same margins and results raises a troubling possibility: that some pollsters are making adjustments in such similar ways that those choices are causing the results to bunch together, creating a potential illusion of certainty — or that some pollsters are even looking to others’ results to guide their own (i.e., “herding”).
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One possibility is that pollsters may sometimes adjust a poll result that looks “weird” to them by choosing a weighting scheme that produces results closer to the results of other polls. There seem to be strong incentives for risk-averse pollsters to do so. Unless a pollster is conducting a lot of polls and they can be sure that the impact of randomness averages out, they may fear reputational and financial costs for getting a result wrong due to randomness, since pollsters are graded on their polling accuracy.