Docs/Market mechanics/Price and probability
Price and probability
Read Buy now, Sell now, spread, midpoint, last trade, and the guarded mark price used by the interface.
Execution quotes#
| Term | Meaning |
|---|---|
| Buy now | Best eligible ask: the lowest price available to a taker buying shares. |
| Sell now | Best eligible bid: the highest price available to a taker selling shares. |
| Spread | Buy now minus Sell now. |
| Midpoint | The average of Buy now and Sell now when both sides exist. |
| Last trade | The latest eligible completed trade, independent of which side initiated it. |
Mark price#
Predistate uses midpoint when both eligible sides exist and the spread is no more than 10 cents. Otherwise it falls back to the latest eligible trade no older than seven days. Levels and trades must meet the configured minimum 1 collateral-unit notional. If neither source qualifies, the mark price is unavailable rather than fabricated.
NO pricing#
NO has its own Buy now and Sell now prices. For mark, midpoint, and last trade, the normalized NO value is 1 − YES. Execution sides are complementary across the opposite side of the YES book, so the spread stays identical.