Prediction markets like Kalshi and Polymarket let you trade directly on real-world outcomes through YES/NO contracts. A YES contract pays out $1 if the event happens and $0 if it doesn’t — simple in theory, but the simplicity hides a lot of ways to lose money.
Buying NO isn’t automatically the smarter play either. The point of this guide is to flag the specific situations where buying YES tends to be a bad trade, even when you genuinely believe the event is likely to happen. If you’re newer to this space, it’s worth pairing this with a broader primer on common mistakes new traders make before you put real money on the line.
1. When the Price Already Reflects Near-Certainty
If a YES contract is trading at 95–99 cents, the market has already priced in a very high probability of the event happening. Your maximum upside is a few cents on the dollar, but your downside is losing the entire stake if the “sure thing” doesn’t come through.
This is a version of the classic favorite-longshot bias in reverse: extreme favorites are often overpriced relative to their true odds, because traders pile in on “obvious” outcomes without demanding enough compensation for the small-but-real chance of an upset. Unless you have a specific reason to think the true probability is even higher than the quoted price, the risk/reward on a 97-cent YES contract is rarely worth it.
2. When You Don’t Have an Edge Over the Market Price
The market price is a collective probability estimate, produced by everyone trading, weighted by how much money they’re willing to put behind their view. If your own estimate matches the market’s, buying YES adds no expected value — you’re just paying the spread and fees for the privilege of taking on risk.
Before buying, ask yourself: do I know something, or think about this differently, in a way that most other traders in this market don’t? If the answer is no, you’re not trading on an edge — you’re gambling on your own confidence. Traders who consistently profit tend to have a repeatable process for spotting where the crowd is wrong, rather than a gut feeling about a single event. If you want to see what that process actually looks like in practice, it’s worth reading through how experienced traders go about finding mispriced prediction markets rather than reacting to headlines.
3. When Liquidity Is Thin
Some contracts, especially on niche or newly listed events, have wide bid-ask spreads and few active traders. In these markets:
- You may pay a premium just to enter the position.
- Exiting early — before the event resolves — can be difficult or costly if you change your mind or need the capital back.
- Prices can be pushed around by a single large trade, meaning the displayed “market price” isn’t a reliable signal of true probability.
Low liquidity turns a directional bet into a liquidity bet — you’re now also wagering that you’ll be able to get out on decent terms if you need to. This is especially relevant on smaller platforms or on contracts covering obscure events where volume never really builds up.
4. When the Time Horizon Is Long
A YES contract that resolves in ten months ties up capital for ten months. Even if you’re confident in the outcome, that capital has an opportunity cost — it could be earning interest elsewhere, funding other trades, or sitting in reserve for better opportunities that show up in the meantime.
The relevant question isn’t just “will this resolve YES?” It’s “is this the best use of this money for this length of time, compared to everything else I could do with it?” A modestly positive expected-value trade that locks up capital for a year can easily be worse than a smaller-edge trade that resolves in a week and lets you redeploy.
5. When You’re Trading on Emotion or Confirmation Bias
If you want an outcome to happen — your candidate to win, your team to make the playoffs, your prediction to be validated — it’s easy to unconsciously inflate your probability estimate to justify a trade you already wanted to make. This is one of the most common ways people lose money in prediction markets: they’re not pricing the event, they’re pricing their own hope.
A useful gut-check: would you take the identical trade, at the identical price, if the event were something you had no emotional stake in? If the honest answer is no, that’s a signal to sit the trade out, not to size up.
6. When the Resolution Criteria Are Ambiguous
Some contracts have resolution rules that sound clear but turn out to have edge cases — what counts as “official,” which data source is authoritative, what happens if the event is postponed, redefined, or only partially occurs. If you’re not sure exactly how and when a contract resolves, you’re taking on a hidden layer of risk that has nothing to do with your view of the underlying event.
This matters more than most new traders assume. Contracts have resolved in ways that surprised confident YES holders simply because the fine print defined the event differently than the headline question implied. Before putting money into any contract with even slightly unusual wording, it’s worth spending five minutes on reading the fine print on resolution rules rather than assuming the plain-language question is the whole story.
7. When Fees and Spreads Eat Most of the Expected Value
Trading fees are usually small in absolute terms, but relative to a thin edge they can matter a lot. If your estimated edge is 2–3 percentage points and the platform’s fees and spread cost you 1–2 points, you’ve given away most of your expected profit before the contract even resolves.
This especially matters for high-probability YES contracts, where the dollar amount at risk is large relative to the potential gain. A trade that looks profitable on paper can quietly turn negative once real-world execution costs are factored in — which is exactly why disciplined position sizing matters. Betting a consistent, risk-adjusted amount on every idea, rather than a flat stake regardless of conviction, is one of the simplest ways to keep fee drag from outweighing a genuine edge.
8. When It Concentrates Risk You Already Have Elsewhere
If a YES contract’s outcome is correlated with other bets, investments, or personal financial exposure you already carry — for example, buying YES on an economic outcome that would also affect your job, your industry, or your portfolio — you may be adding correlated risk rather than diversifying. A trade that looks attractive in isolation can be a bad idea in the context of your overall exposure.
This is easy to overlook because prediction market contracts feel self-contained: you’re just betting on one question. But money is fungible, and a loss on a YES contract that coincides with a downturn elsewhere in your finances hurts more than the contract’s face value suggests.
The Common Thread
None of these eight situations are reasons to avoid prediction markets altogether — they’re reasons to be selective about which YES contracts you actually buy. The pattern running through all of them is the same: buying YES makes sense when you have a genuine, reasoned edge over the market price, adequate liquidity to act on it, clear resolution terms, and a clear-eyed view of your own biases and overall risk exposure. When any of those is missing, the trade starts to look less like an informed position and more like a lottery ticket with extra steps.
Before your next trade, run through the list: Is the price already near-certain? Do I actually have an edge, or am I just agreeing with the crowd? Is there enough liquidity to exit if I need to? Am I comfortable tying up this capital for this long? Am I trading the event, or trading my own hope? Do I understand exactly how this resolves? Have fees eaten my edge? And does this add risk I already carry elsewhere? If any answer gives you pause, that’s usually the market telling you something worth listening to.
FAQ
1. Is it ever a good idea to buy a YES contract priced above 95 cents?
Sometimes, but only if you have a specific reason to believe the true probability is even higher than the market price — for example, new information the market hasn’t fully absorbed yet. Without that edge, the small potential gain rarely justifies the risk of losing the full stake.
2. How do I know if a prediction market has enough liquidity to trade safely?
Check the bid-ask spread and the total volume or open interest on the contract. A wide spread or very few visible orders on either side is a sign that entering — and especially exiting — the position could cost you more than the quoted price suggests.
3. What’s the difference between buying YES and buying NO on the same contract? They’re mirror images of the same market: buying NO is economically similar to selling YES. The same principles in this article — checking for an edge, understanding resolution rules, watching liquidity — apply symmetrically whichever side you’re on.
4. Can resolution criteria really change the outcome of a contract I was confident about?
Yes. Contracts settle based on their exact written rules, not the plain-language headline. Edge cases around timing, data sources, or how an event is officially defined have surprised traders who assumed the outcome was obvious.
5. How much of my portfolio should go into a single YES contract?
There’s no universal number, but disciplined traders size positions based on their estimated edge and confidence rather than betting a flat amount on every idea. Position sizing matters more as the price gets closer to certainty, since the potential loss (the full stake) stays fixed while the potential gain shrinks.
Colin is a long-time digital media channel operator and content creator with an intense interest in sports gaming, prediction markets, and artificial intelligence, and how they are shaping the social, entertainment, and economic landscapes.
