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.
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!