Methodology

What The Feed Publishes

For each covered candidate contract, PredictionMarketOdds.com publishes one hourly probability print. Each print uses the preceding 60-minute window and is rounded once to the nearest 0.001.

If fewer than two venues qualify for a candidate in a window, the feed publishes no number for that candidate and marks it NO_PRINT.

Sampling

Each venue is sampled about once per minute. The sampler records executable order-book evidence for each candidate: the price to buy a fixed reference notional of YES, the price to sell the same notional, the resulting mark, the spread, the depth near the mark, and whether the sample passed validity checks.

The scheduler records the randomness source used to choose each minute's sample second. When public drand randomness is reachable, the print document includes the drand rounds and signatures used by the scheduler.

Venue Mark

A venue sample uses an executable impact-mid mark:

mark = (buy price at Q + sell price at Q) / 2

The current reference notional is $250 per side. A sample is valid only if both sides can fill the reference notional and the executable spread is no more than 8 percentage points, or 12 points near certainty when the previous print was below 5% or above 95%.

Freshness

When a venue provides a source timestamp for its order book or market-book snapshot, that timestamp must be within 60 seconds of the fetch time. Stale timestamped snapshots are stored as evidence but excluded from the calculation.

Some public REST endpoints provide a current snapshot without a separate exchange update timestamp. Those samples are labeled as fetch-time based in the raw evidence.

Venue Median

For each venue and candidate, the feed takes the median of that venue's valid marks within the 60-minute window. A venue must have at least 20 valid samples in the window to qualify.

Weighted Median

For candidates with three or more qualifying venues, the feed uses a weighted median across venue medians.

Methodology: line qualifying markets up from lowest odds to highest. Add each market's weight, based on liquidity, in that order. The print is the first venue where "weight reached" is at least 50%.

With exactly two qualifying venues, the feed uses a weighted mean and marks the print TWO_VENUE.

Weights

Venue weights are based on executable depth, not trade volume. Depth is measured as two-sided capital at risk within 2 percentage points of the mark and averaged over a trailing 24-hour lookback that is lagged by one hour.

The liquidity score is log(1 + depth / 1000). Weights are normalized, capped at 35%, and venues below 2% are dropped after normalization.

Publication

Every print document includes the window, candidate, venue medians, venue weights, flags, a hash chain pointer, and a self-hash. If an Ed25519 signing key is configured, the document includes an Ed25519 signature over the self-hash; otherwise the signature field clearly marks the document as unsigned.