Prediction markets vs.
sports betting

The Core Structural Difference

The single most important thing to understand about prediction markets is what they are not: they are not sportsbooks. This distinction is not semantic. It is mechanical, mathematical, and consequential for every trader who participates.

In a sportsbook, the bookmaker is your counterparty. They set the odds with a built-in profit margin (the vig). When you bet, you are betting against a business whose entire model is to extract a fixed percentage from you on every transaction. There is no amount of skill or strategy that eliminates this edge in the long run — it is baked into the pricing before the line even goes up.

In a prediction market, you are trading against other participants. The platform collects a small fee on executions, but the prices are set by the collective action of everyone in the market — including retail traders making biased, emotional decisions. Your edge does not come from outperforming a mathematical house. It comes from being more rational than the crowd.

The Vig vs. The Taker Fee

How the Vig Works

In sports betting, the "vig" (vigorish) or "juice" is the commission baked into the odds. On a standard even-money bet, most sportsbooks offer odds of -110 on both sides: you must risk $1.10 to win $1.00. This means if 50% of bettors are on each side, the book collects $2.20 in bets and pays out only $2.00 — keeping 20¢, or approximately 4.5–9.1% of the total handle.

The Kalshi Taker Fee Formula

Kalshi's taker fee is not a flat percentage — it is dynamic, calculated as:

Long-Run Returns: The Reality

Neither environment is kind to undisciplined retail participants. But the ceiling is fundamentally different:

• Sports bettors: Approximately 2–3% of sports bettors are net profitable long-term. The house edge is a permanent, compounding tax on every bet.
• Prediction market traders: Research across 112,000 Polymarket wallets found 87.3% of users lose money. A separate study (Reichenbach & Walther, 2025) analyzing 124 million trades concluded only 30% of traders generate positive profits.

A 12.7–30% profitability rate is significantly better than the sportsbook equivalent. More importantly: the unprofitable majority in prediction markets are losing to the profitable minority, not to a house. Their losses are someone else's gains. That someone else can be you, if you operate systematically.

Pari-Mutuel vs. Central Limit Order Book

Understanding this distinction clarifies why prediction markets allow price-locking that sportsbooks and pari-mutuel betting cannot offer.

Pari-mutuel betting (horse racing): All bets of a given type pool together. The house takes its cut, and the remainder is divided among winners. Crucially, you don't know your final payout until the betting window closes. If everyone bets on the same horse after you, the odds shorten and your expected return decreases.

Prediction markets (CLOB): Kalshi and Polymarket both operate Central Limit Order Books. You lock in your price — and therefore your exact implied probability and payout — the moment your order fills. If you buy YES at 30¢, that's your entry regardless of what happens to the market price afterward.

The Legal Landscape

Kalshi: Fully Regulated, US-Legal

Kalshi is a Designated Contract Market (DCM) regulated by the US Commodity Futures Trading Commission (CFTC) under the authority of the Commodity Exchange Act. It received regulatory approval in 2020 and has been operational since 2021. It is legally compliant across all 50 US states.

The CFTC classification matters: Kalshi's contracts are treated as financial instruments (event contracts), not as bets. This regulatory structure is why Kalshi can operate openly in the US while offshore platforms cannot.

Polymarket: Offshore, US-Restricted

Polymarket is based in Panama and uses geoblocking to restrict US access. In 2022, Polymarket paid a $1.4 million penalty to the CFTC for operating an unlicensed exchange and agreed to block US users as a condition of settlement.

In late 2025, Polymarket began rolling out a US-only sports app via its acquired entities QCX LLC and QC Clearing LLC, which received limited CFTC approval for sports event contracts only. This is separate from the main global Polymarket platform.

Taxes: Event Contracts, Not Gambling

Prediction market platforms argue their products are event contracts — financial instruments regulated as futures, not gambling instruments. This distinction has practical tax implications:

• By classifying themselves as commodity futures markets, platforms like Kalshi position participant gains as potentially subject to capital gains treatment rather than gambling-specific withholding rules
• The legal classification has helped these platforms avoid state gambling taxes and age verification requirements that apply to traditional sportsbooks
• However, this area remains unsettled law. Consult a tax professional for guidance specific to your situation

What the research consistently shows: the platforms are designed to be treated as financial exchanges. Treat your prediction market activity accordingly — track entries, exits, and fees with the same rigor as any investment account.