# Polymarket efficiency: two tests, updated monthly

On PredictIt, the bids on every outcome of a busy market added up to 110 to 125¢. On Polymarket the typical event adds up to 87¢, and long shots win more often than their price says. Two tests, rerun every month.

Canonical URL: https://vultax.com/research/efficiency-series
Author: [Vultax Research](https://vultax.com/editorial-policy)
Published: 2026-10-16
Last public revision: 2026-10-16

Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Monthly research snapshots with dated observations and separate samples. Implementation gaps and historical quote limitations are documented in the methods.

## Key figures

- Typical bid sum across every outcome: 87¢ — Median of the 61 Polymarket events where every outcome had a bid, 15 October 2026. PredictIt's busiest markets summed to 110 to 125¢.
- Favourite-longshot slope: 0.91 — 3,663 contracts in 1,298 events, January 2025 to September 2026, bootstrap range 0.84 to 0.97. Below 1 means long shots won more often than their price said.
- Release cadence: Monthly — Observation dates, completed releases and the next scheduled run are shown separately.
- First public release: 16 October 2026 — The underlying observations retain their own measurement dates.

<a id="two-tests"></a>
## Two questions, followed over time

The first test adds the displayed Yes bids across all listed outcomes of an eligible Polymarket event. The second compares historical prices with later outcomes using a favourite-longshot calibration regression. The interactive series presents the current release and the same slope month by month.

[Open the charts and monthly record](https://vultax.com/research/efficiency-series). Each observation keeps its measurement date; the next scheduled release is distinct from a completed update.

### Bids on every outcome, added up: 61 Polymarket events, 15 October 2026

Events by the sum of the best Yes bids across all their outcomes, in 10¢ bands from the value shown. None reached 100¢. PredictIt's busiest markets summed to 110 to 125¢ in 2019 to 2022.

| Category | Polymarket events |
| --- | --- |
| <60¢ | 8 |
| 60¢ | 5 |
| 70¢ | 9 |
| 80¢ | 12 |
| 90¢ | 27 |
| 100¢+ | 0 |

[CSV](https://vultax.com/research/efficiency-series/data.csv?dataset=two-tests-chart), [JSON](https://vultax.com/research/efficiency-series/data.json?dataset=two-tests-chart)

<a id="methods"></a>
## Read the definitions alongside the results

These are related tests with explicit implementation gaps, rather than an exact replication or a matched comparison with the historical PredictIt study. Baskets with a bid on every outcome and the secondary missing-bid convention have separate denominators. Historical prices are read relative to scheduled end, with the original exclusions retained.

The [method note](https://vultax.com/research/efficiency-series/methods.html) documents the samples, fees, timing, uncertainty and limitations. Dated reproducibility packages are linked from the series.

<a id="related-research"></a>
## Related Vultax research

Read the separate studies of [Polymarket price calibration](https://vultax.com/research/prediction-market-fair-value-calibration) and [deadline-market accuracy](https://vultax.com/research/polymarket-deadline-markets-accuracy). Their populations and observation windows differ from this continuing series.

## Sources and methodology

- [Efficiency-series methods and source map](https://vultax.com/research/efficiency-series/methods.html) — Definitions, paper references, implementation gaps and reproducibility details.