How many participants does a manifold market need to become sufficiently predictive (80% probability of being right)?
46
Never closes
1-4
5-19
20-49
50-99
100+

Get
Ṁ1,000
and
S3.00


Sort by:
10mo

Technically, a market is never "right," as more predictors could still make it more precise (unless it has reached 100% or 0% for something with a guaranteed outcome). However, I have a hard time otherwise defining "sufficiently predictive." My convoluted working definition is "at least 80% of markets with this number of participants are within 5% of the asymptotic value as the number of participants approaches infinity."

1y

Depends on the market, but most stabilize around 5-10 traders in (especially if they're about niche topics that a small number of people have a very large interest in.)

1y

80% probability of being right (if by right means that it is above 50% if it happens and below 50% if it does not happen) is a pretty low bar. Many things are so close to 100% and 0% that a single person could easily get above 80% with some selective betting.

1y

@SophusCorry I mean an 80% chance that a market resolves with the implied probability. For example markets with a 70% chance to resolve as YES will have a 70% chance of resolving YES at least 80% of times.
Which makes me think that we should probably factor in time dependencies here, since predictions will be a lot more accurate right before the occurence of an event, but also a lot less useful.
A more precise question might be: "What is the minimum number of participants at which a median manifold market at its half time will resolve at least 80% of the time with the agreed upon chance"
Or something like that. I wrote myself in a corner here.

1y

if you look at https://calibration.city/manifold the calibration is pretty good after 5 traders, even with a low number of trades, though at there is a bias where the numbers are closer to 50% than what they should be

1y

@NihilCranes I guess that makes the poll obsolete

1y

@Symmetry nah it's still a good question

What is this?

What is Manifold?
Manifold is the world's largest social prediction market.
Get accurate real-time odds on politics, tech, sports, and more.
Win cash prizes for your predictions on our sweepstakes markets! Always free to play. No purchase necessary.
Are our predictions accurate?
Yes! Manifold is very well calibrated, with forecasts on average within 4 percentage points of the true probability. Our probabilities are created by users buying and selling shares of a market.
In the 2022 US midterm elections, we outperformed all other prediction market platforms and were in line with FiveThirtyEight’s performance. Many people who don't like trading still use Manifold to get reliable news.
How do I win cash prizes?
Manifold offers two market types: play money and sweepstakes.
All questions include a play money market which uses mana Ṁ and can't be cashed out.
Selected markets will have a sweepstakes toggle. These require sweepcash S to participate and winners can withdraw sweepcash as a cash prize. You can filter for sweepstakes markets on the browse page.
Redeem your sweepcash won from markets at
S1.00
→ $1.00
, minus a 5% fee.
Learn more.
© Manifold Markets, Inc.Terms + Mana-only TermsPrivacyRules