# Good Judgment Open

Brier scores against the crowd, and the recruiting ground for Superforecasters.

*https://predictionmarkets.tools/tools/good-judgment-open · Forecasting Platforms*

## Facts

### At a glance

| Field | Value |
| --- | --- |
| Vendor | Good Judgment |
| Category | Forecasting Platforms |
| Job | tournaments |
| Website | https://www.gjopen.com |
| Pricing model | free |
| Free tier | true |
| Open source | false |
| Licence | none |
| Self-hosted | false |
| Tested hands-on | false |
| Last updated | 2026-09-19 |

### Availability

| Field | Value |
| --- | --- |
| Jurisdictions | global |
| Open to US persons | true |
| KYC required | false |

### Markets

| Field | Value |
| --- | --- |
| Subjects | politics, macro, science, business, sports, culture |
| Settlement | play_money |
| Resolved by | Credible open-source evidence and media reporting unless the question names a specific source, with Good Judgment reviewing a named source for plain error before resolving against it. |

### Economics

| Field | Value |
| --- | --- |
| Taker fee | none |
| Maker fee | none |
| Liquidity model | none |
| Platforms | web |
| AI features | none |

### Interfaces

| Field | Value |
| --- | --- |
| API | false |
| WebSocket | false |
| Scripting | none |
| Python | false |
| MCP server | false |
| Export | none |

### Capabilities

Yes: charting, calibration_scoring, alerts

No: screening, order_book, backtesting, automation, live_trading, paper_trading, portfolio_tracking, cross_venue, news, tax_reporting

*Verified: pricing 2026-09-19; availability 2026-09-19; markets 2026-09-19; capabilities 2026-09-19.*

## What it is

A free public forecasting site owned and operated by Good Judgment, the firm that grew out of the
Good Judgment Project — the team that won the US government's ACE forecasting tournament and that
Philip Tetlock's *Superforecasting* is about. You forecast probabilities on questions grouped into
Challenges, each Challenge has a leaderboard, and everything about the design points at one number.

That number is the **Relative Brier Score**, and it is the reason to read this card rather than
assume the site is a slower Metaculus. A Brier score is the squared error of a probabilistic
forecast, from 0 (perfect) to 2 (as wrong as possible), computed for every day you had a live
forecast and then averaged. Good Judgment reports three figures beside each question: your Brier
score, the **Median Score** — the median of everyone's daily Brier scores on that question — and
the Relative Brier Score, which is your average daily Brier minus the crowd's average daily median,
multiplied by your Participation Rate. Lower is better throughout, negative means you beat the
crowd, and a question you skipped scores zero rather than penalising you.

Two consequences of that formula are worth knowing before you start. Because it multiplies by the
share of days you were in, arriving late with the right answer is worth less than being roughly
right early and updating. And because it is a difference against the crowd rather than an absolute
number, the only way up a Challenge leaderboard is to be better than the people standing next to
you on the same questions. Note that this is not zero-sum in the arithmetic sense a Metaculus Peer
score is: the subtraction here is against the crowd's median rather than its mean, and it is scaled
by each forecaster's own participation, so the scores on a question do not cancel out to nothing.

You cannot withdraw a forecast or delete one, by policy, so that nobody can tidy their record
after the fact.

### Its relationship to Good Judgment the firm

These are two products and this card is about one of them. Good Judgment sells FutureFirst, custom
Superforecasts, training and UK government services to corporate, government and NGO clients, and
those run on its own platforms with the roughly 180 professional Superforecasters it says it works
with. GJ Open is the open site, free to anyone, and the firm is explicit on its own pages that it
is also the recruiting funnel: each autumn it identifies potential Superforecasters from among GJ
Open forecasters who have answered at least 100 questions, looking hardest at average accuracy per
closed question, then at comment quality and collegiality, with a three-month probation at the end.

It is also sold to organisations as a place to run private or public Challenges for talent-spotting
and training. So a Challenge you join may have a sponsor with an interest in it — the site names
UBS Asset Management, The Economist and Harvard Kennedy School among Challenge sponsors on its own
front page.

## Availability

Open worldwide and free. The terms of service require you to be 18 or over, are governed by New
York law, route disputes to arbitration in New York, and state that using the service consents to
your personal data being transferred to and processed in the United States. There is no identity
check, nothing to deposit, and no jurisdictional geoblock of the kind a venue has, because there is
no money involved at any point.

## Pricing

Free to forecast, free to read, no paid tier for individuals. Good Judgment's revenue comes from
its commercial services and from organisations commissioning Challenges — not from forecasters.

Some Challenges carry a prize, and the prize is usually recognition rather than cash: the Economist
Challenge publishes its winner in *The Economist*, and the site awards permanent badges to the top
20% by Relative Brier Score in several annual Challenges. Eligibility rules are per Challenge and
can be demanding — the 2026 Economist Challenge required forecasts on at least 22 of the roughly 25
questions to be eligible to win.

## Markets & resolution

Geopolitics and armed conflict, elections worldwide, macro and central bank data, energy, AI, and a
long tail that includes awards season and football management. Active Challenges as of 19 September
2026 included the 2026 US Midterms, The Economist's World Ahead 2026, Global Armed Conflict in
2026, Artificial Intelligence in 2026 and Beyond, a Federal Reserve Economic Data challenge, a
purchasing managers' index challenge, and a Harvard Kennedy School teaching challenge.

Resolution is Good Judgment's and its documentation of it is unusually detailed. Unless a question
names a source, it resolves on credible open-source evidence and media reporting, with credibility
assessed by corroboration and reputation. Where a question names a source, Good Judgment reserves a
review for plain error — its worked example is an FAO publication that overstated Pakistani data by
a factor of a thousand and was corrected after they asked. Questions close on when an event
occurred rather than when it was reported, which means retroactive closing dates are normal and
only forecasts made through the calendar day before the official close are scored. Ordered
categorical questions get a special scoring rule so that a near-miss on a sequential range is not
treated as identical to being wrong by an order of magnitude. Open questions, which invite
discussion without a forecast, are never scored.

## Integrations

There are none, and that is a fact about the product rather than an omission from this card. Good
Judgment publishes no API, and the terms of service explicitly do not grant permission for
collection, aggregation, copying or derivative use of the site, nor for data mining, robots,
spiders or similar extraction tools, without written permission. The platform is built and run on
Cultivate Labs software, the same vendor behind several institutional forecasting programmes, but
that is the operator's choice rather than anything you can build against.

If your reason for being here is to get forecast data out, this is the wrong card in this category.

## Limitations

No data out, no automation, no bots. Everything above is deliberate, and it makes GJ Open unusable
as a source for anything downstream.

The scoring is relative to the crowd on the same questions, which makes cross-Challenge comparison
of Relative Brier Scores meaningless and makes the number incomparable with a Metaculus Peer score
despite both being crowd-relative — one is built on Brier, the other on the log score, and the two
punish confident errors differently.

Question flow is set by Good Judgment and its Challenge sponsors, so the subject matter tracks what
a forecasting firm and its clients care about. If the question you want forecast is not in a
Challenge, your options are to suggest it and wait.

And the incentive at the top of the leaderboard is a job application. That is a real incentive and
an honest one, but it is worth knowing that the people you are scored against include a cohort
trying to get hired.

## Alternatives

[Metaculus](https://predictionmarkets.tools/tools/metaculus) for a proper scoring rule, an open codebase and — with a token —
programmatic access. [Manifold](https://predictionmarkets.tools/tools/manifold) if you want volume, speed and the ability to list
your own question, at the cost of a stranger resolving it.

## FAQ

### Is Good Judgment Open the same thing as Good Judgment Inc?

No. Good Judgment Open is the free public forecasting site. Good Judgment is the firm that owns and operates it and separately sells FutureFirst, custom Superforecasts, training and government services. This card is about the open platform, which is the only one a reader can simply join.

### How is a forecast scored on Good Judgment Open?

By Brier score, averaged across every day a forecast stood. Three numbers are reported — your Brier score, the crowd's median score, and the Relative Brier Score, which subtracts the median from yours and multiplies by the share of days you had a forecast in. Lower is better and negative beats the crowd.

### Can you become a Superforecaster through the site?

That is the stated route. Good Judgment recruits each autumn from forecasters who have answered at least 100 GJ Open questions, weighing average accuracy per closed question most heavily, plus comment quality and collegiality, followed by a three-month probation.

### Does Good Judgment Open have an API?

None that it publishes. The terms of service go further and withhold permission for collection, aggregation or derivative use of the site, and for data mining, robots, spiders or similar extraction tools, without written permission.

## Background

- [Scientific and government forecast hubs](https://predictionmarkets.tools/guides/scientific-forecast-hubs.md) — Public-health agencies run open, scored forecast hubs anyone can join. The unit of submission is a model, not a person, and nothing there is a personal record.
- [What a forecasting platform's score actually measures](https://predictionmarkets.tools/guides/what-a-forecasting-score-measures.md) — Proper rules, the two Brier conventions that differ by a factor of two, crowd-relative scores that do not travel between sites, and why profit is not accuracy.
- [How accurate a prediction market's price actually is](https://predictionmarkets.tools/guides/how-accurate-the-price-is.md) — What research establishes about reading 73 cents as a 73% chance — where market prices are calibrated, the deviations that recur, and what the horizon does.

## Also worth comparing

- [Hypermind](https://predictionmarkets.tools/tools/hypermind.md) — Play money, a real order book, and a few thousand euro of prizes split by performance.
- [Confido](https://predictionmarkets.tools/tools/confido.md) — Open-source forecasting workspace you host yourself, with a Brier score pointing upwards.
- [Fatebook](https://predictionmarkets.tools/tools/fatebook.md) — Write down what you think will happen, in Slack or a browser, and get scored on it.
- [Manifold](https://predictionmarkets.tools/tools/manifold.md) — Anyone can open a question, anyone can take a side, and the currency buys nothing.
- [Metaculus](https://predictionmarkets.tools/tools/metaculus.md) — Proper scoring and public track records on questions nobody can take a position in.
- [Prediki](https://predictionmarkets.tools/tools/prediki.md) — A wiki with a market attached — anyone writes the question, edits it, votes the result.

## Named as a replacement for

- [INFER](https://predictionmarkets.tools/alternatives/infer.md)