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Predict 0.1%—99.9% With Decimal Forecasting

Metaculus Meta

Decimal Forecasting

Forecasters have long sought the ability to predict low-probability events below the 1% threshold. We're excited to introduce a new capability that enables just that. Decimal forecasting means you can predict probabilities as high as 99.9%, as low as 0.1%, and every tenth of a percent in between.

decimalforecasting

How Does It Work?

On desktop, hover over the prediction slider to reveal arrows. Click one to adjust your forecast by 0.1%. (On mobile, the arrows are always visible.)

Dragging the slider only selects between integer probabilities, just like before.

Watch Your Score: Tail Risks

With great precision comes great responsibility. While the math behind Brier, log, and tournament scoring has not changed,  incorrect 99.9% and 0.1% predictions result in significantly worse log and tournament scores relative to 99% and 1% predictions, whereas correct predictions score only slightly better.

Scoring remains proper, so predicting your true beliefs is still the best strategy. If the true probability is 0.1%, you will maximize your score over many questions by predicting 0.1%. 

Make Some Finer Forecasts

Here are a few questions where more precision could be useful:

All Decimal Systems Go

Decimal forecasting is valuable on its own, and it's also a step toward additional exciting improvements. 

We're always keen to hear your opinions and ideas — please share your feedback on decimal forecasting in the comments below, and tell us what else you'd like to see in the future!

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