#### Your submission is now in Draft mode.

Once it's ready, please submit your draft for review by our team of Community Moderators. Thank you!

#### Your essay is now in Draft mode

Once you submit your essay, it will be available to judges for review and you can no longer edit it. Please make sure to review eligibility criteria before submitting. Thank you!

Submit Essay

Once you submit your essay, you can no longer edit it.

#### Pending

This content now needs to be approved by community moderators.

#### Submitted

This essay was submitted and is waiting for review by judges.

# Will a prediction market outperform Nate Silver's forecasts for the Super Tuesday primaries?

### Question

Nate Silver has achieved significant notoriety for developing a system to carefully aggregate election polls to create well-calibrated statistical forecasts of outcome elections; his site publishes daily updates to predictions for primary and general elections in House, Senate and Presidential races.

Prediction markets have offered an alternative to poll aggregation in forecasting elections. Markets such as (the now defunct) InTrade, the Iowa Electronic Markets, PredictIt, and others ask users to buy and sell shares assigned to each candidate in each race, so that the price point corresponds to the probability of victory. In this question we focus on PredictIt, which allows users to place relatively small real-money bets on candidates.

Both fivethirtyeight.com and PredictIt have published probabilities for each of the 11 Super Tuesday Primaries on both the Republican and Democratic side.

Which forecasts will prove to be more accurate?

To compare, we will score each set of predictions using a Brier score averaged over all $N=22$ races, computed as where j enumerates the $M_i$ possible outcomes (i.e. possible winners) in the ith race out of N, where $p_{ij}$ is the forecast probability of candidate j winning the ith race, and $o_{ij}$ is assigned 1 if candidate j wins the ith race, and 0 otherwise.

For example, PredictIt assigns (as of writing) 52% to Clinton and 48% to Sanders in the Minnesota Democratic Primary. If this were the only primary, and Clinton won, PredictIt would achieve a Brier Score of A lower Brier score is better, with perfect predictions corresponding to $S=0$. (In the case where PredictIt's prices do not add up to $1, we will normalize them to$1 to convert to probabilities.)

This question resolves positively if the Brier score for the 22 races is lower for PredictIt's probabilities than for fivethirtyeight.com's probabilities, where we will take values as of noon EST on 2/29/2016, and election outcomes as reported on 3/1-3/2.

Categories:
Politics – US

### Prediction

Note: this question resolved before its original close time. All of your predictions came after the resolution, so you did not gain (or lose) any points for it.

Note: this question resolved before its original close time. You earned points up until the question resolution, but not afterwards.

This question is not yet open for predictions.

Current points depend on your prediction, the community's prediction, and the result. Your total earned points are averaged over the lifetime of the question, so predict early to get as many points as possible! See the FAQ.

### Metaculus help: Predicting

Predictions are the heart of Metaculus. Predicting is how you contribute to the wisdom of the crowd, and how you earn points and build up your personal Metaculus track record.

The basics of predicting are very simple: move the slider to best match the likelihood of the outcome, and click predict. You can predict as often as you want, and you're encouraged to change your mind when new information becomes available.

The displayed score is split into current points and total points. Current points show how much your prediction is worth now, whereas total points show the combined worth of all of your predictions over the lifetime of the question. The scoring details are available on the FAQ.

#### Thanks for predicting!

Your prediction has been recorded anonymously.

Want to track your predictions, earn points, and hone your forecasting skills? Create an account today!