What does a probability on a prediction market mean?

The percentage beside each outcome on a PredictX market is the PredictX probability. It is computed from the tokens committed to the market: on a two-outcome market it is smoothed toward 50% while the pool is small, and with three or more outcomes it is each outcome’s share of the tokens still in contention.

So it measures commitment. A 70% outcome is one the pool has backed heavily; it is not a statement by PredictX about what will happen.

A probability is not a guarantee. An outcome at 70% should still lose about three times in ten — if outcomes at 70% never lost, the figure would be too low, not impressively accurate.

It is also not a forecast or a tip. PredictX does not endorse the figure or stand behind it; it is a reading of what has been committed, and it can be wrong.

The useful test of a crowd is calibration: across many settled questions, do the outcomes it favoured at about 70% win about 70% of the time? A crowd can be right on a single question by luck. It shows whether it is any good only over many.

PredictX publishes this test for its players on the crowd accuracy page: how often the outcome players favoured actually won, grouped by how strongly they favoured it, with the number of markets behind every rate.

Where a market shows what players favoured, that figure is the split of players’ own tokens, counted from player accounts only and shown only once enough players have predicted. The PredictX probability is computed from the whole pool. The two usually agree in direction but are different measurements, and PredictX labels them separately.

A market with a handful of predictions says little. Smoothing keeps a two-outcome market near 50% until tokens accumulate, and player figures are withheld until there are enough players to describe a crowd rather than an individual. Treat an early figure as provisional.

Call it the PredictX probability, give the time it was read — an open market page states it — and link the market page. An open market changes continuously, so a figure without a time is unfalsifiable.

For anything settled, quote the settled market page: it states the result, the final PredictX probability and the date the market settled, and once the dispute window has closed and any dispute raised within it has been decided, it does not change again.