The Election Prediction Fallacy

In the late stages of the Vietnam War, public opinion pioneer Daniel Yankelovich came up with a theory he called the McNamara Fallacy. The gist is that over-relying on certain data creates blind spots in decision-making. As Yankelovich wrote:

The first step is to measure whatever can be easily measured. This is OK as far as it goes. The second step is to disregard that which can't be easily measured or to give it an arbitrary quantitative value. This is artificial and misleading. The third step is to presume that what can't be measured easily really isn't important. This is blindness. The fourth step is to say that what can't be easily measured really doesn't exist. This is suicide.

McNamara Fallacy

We are seeing the McNamara Fallacy at work in the media-based election prediction industry, presently focused on the midterms. A basic problem is that opinion polls are not designed to predict things, they are designed to give a snapshot of opinion at a moment in time. Even in the highest-information election cycles, many voters don't make up their minds until the final days of an election, undercutting the value of predicting things weeks or months in advance.

A larger problem involves the many difficult-to-measure variables shaping today's political context, from a society-altering global pandemic to a seismic partisan realignment reshaping both political parties. Old models for understanding politics, like the paramount importance of presidential approval on midterm outcomes, may not hold. The bottom line is this: we do not know what is going to happen, and we have to get comfortable with uncertainty.

So how do you navigate the next five days? If you're open to partisan involvement, get out and knock on doors or make phone calls for a candidate. If you want to know how to make sense of the today's environment, start with Pew's Political Typology Report, which classifies the American public into nine groups based on values and attitudes. Understanding the forces shaping our politics provides helpful distance from whiplash-inducing news of the day.

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The Why of the Midterms — and What's to Come

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Hmm, Do I Hop Out and Vote?