Market efficiency
Updated November 10, 2026
Market efficiency is the idea that prices incorporate available information, not that prices are always “correct.” Efficient enough markets are hard to beat after fees; inefficient pockets can exist in thin or newly listed contracts.
Minutes before a CPI release, a “above 3.0%” contract trades 62¢. After a hot print, it jumps to 88¢. The move reflects new public information, classic efficiency in action. A thin awards-market contract stuck at 40¢ despite obvious news may be inefficient until liquidity arrives.
- “Above 3.0%” minutes before the CPI release
- 62¢
- The same contract after a hot print
- 88¢
- Thin awards contract despite obvious news
- 40¢
- May be inefficient until liquidity arrives
Weak, semi-strong and strong forms
The standard framing, borrowed from equity markets, splits efficiency by what kind of information prices are said to reflect:
- Weak form. Prices reflect past prices, so a chart pattern alone shouldn’t predict the next move.
- Semi-strong form. Prices also reflect all public information, and adjust quickly when new public information arrives.
- Strong form. Prices reflect private information too. This version is generally treated as too strong to hold in practice.
The CPI contract in the example, moving from 62¢ to 88¢ on a public release, is the semi-strong form at work. The thin awards contract that stays put despite obvious public news is failing that test, at least until traders arrive.
What efficiency does and doesn’t claim
Efficiency is usually framed as a claim about difficulty: after costs, it is hard to do better than the price consistently. That is compatible with the price being wrong on any single question. A contract at 88¢ that resolves no doesn’t show the market was inefficient, since an 88% estimate implies the other outcome about 12% of the time. Whether prices match outcomes over many contracts is a question for calibration.
The conditions the argument depends on show up on a market page: a narrow spread, meaningful volume, time since listing, price moves that line up with public events, and settlement terms that name a specific source. Thin, newly listed or ambiguously worded contracts meet fewer of them. A price that looks inefficient isn’t automatically an opportunity either, because the same thinness widens the spread and makes trading more expensive. Market efficiency in prediction markets covers each condition.
FAQ
Are prediction markets efficient?
It’s a hypothesis, and the conditions it depends on are present in some markets and absent in others. It’s assessed market by market, the same way it is for stocks.
Does market efficiency mean the price is correct?
No. It means the price is hard to beat consistently after costs. A market can meet that standard and still be wrong on a given question.
What are the three forms of market efficiency?
Weak form (prices reflect past prices), semi-strong form (prices reflect all public information) and strong form (prices reflect private information too).