Event contracts are derivatives

Strip away the politics and the sports and an event contract is a plain financial instrument — a binary option on a real-world fact. Here is the financial anatomy.

This series has spent eight parts on what a prediction market does — it prices the future, it aggregates dispersed knowledge, it grades its own forecasts. This part is about what an event contract is. And the answer is older and more boring than the headlines suggest: it is a derivative. The same family as a futures contract or a stock option. Once you see it that way, almost everything about the category stops being mysterious — why it's priced the way it is, why nobody can default on you, and why a derivatives regulator was the one that claimed it.

A derivative is just a contract whose value is derived from something else — the price of oil, the level of an index, whether a candidate wins. An event contract derives its value from a single fact about the world: did the event happen, yes or no. That puts it in a very specific corner of the derivatives universe, the one finance has known about for decades under a slightly unglamorous name.

An event contract is a binary option on a real-world fact. Everything else is detail.

A binary option, by its proper name

The instrument has a textbook name: a binary option, also called a digital option.¹ It pays a fixed amount if a condition is met at expiry, and nothing otherwise. On a prediction market the fixed amount is normalized to $1. Hold a YES contract to expiry and you receive exactly $1 if the event happened and exactly $0 if it didn't. There is no in-between, no "how much" — only "whether."

We can write the payoff with an indicator function — the mathematician's switch that equals 1 when its condition is true and 0 when it's false. If $\mathbf{1}[\,\cdot\,]$ is that switch, the value of one YES contract at expiry is:

$$ \text{payoff} \;=\; \$1 \,\cdot\, \mathbf{1}[\,\text{event occurs}\,] \;=\; \begin{cases} \$1 & \text{event occurs} \\[2pt] \$0 & \text{otherwise} \end{cases} $$

That indicator is the whole personality of the instrument. Plotted against the underlying outcome, the payoff is a step function — flat at $0, then a vertical jump to $1 the instant the condition is crossed. Engineers call that exact shape a Heaviside step; it is the cleanest payoff in finance, a single binary cliff.

Contrast it with a vanilla call option, the thing most people picture when they hear "option." A call pays nothing until the underlying clears a strike, and then pays more and more the further it travels — a sloped "hockey stick," continuous and unbounded on the upside. The binary doesn't care how far. One cent past the threshold or a mile past it, the payoff is the same $1. It has thrown away magnitude and kept only direction.

Fig 1 — the binary pays a flat $1 past the threshold; a vanilla call keeps climbing · illustrative

The price is the probability — again

If you've read Part 3 or Part 4, the next step is familiar, but now it has a name attached. The fair value of a derivative is the expected value of its payoff. For a contract that pays $1 on the event and $0 otherwise, with the event assigned probability $p$, that expectation collapses to almost nothing:

$$ \text{price} \;=\; \mathbb{E}[\text{payoff}] \;=\; (\$1)\cdot p \;+\; (\$0)\cdot(1-p) \;=\; p $$

The price is the probability. A contract at 62¢ is the market quoting a 62% chance. That identity isn't unique to prediction markets — it's the standard way every digital option in the world is valued. The technical caveat is one word, and it's worth saying out loud because it's exactly the bridge to traditional finance: the relevant $p$ is a risk-neutral probability, the probability implied by what people will actually pay, not necessarily their private gut belief.² In a market dominated by small, diversifiable bets the two are nearly identical, which is why "62¢ means 62%" is an honest reading. And to be fully correct you discount for time value — a dollar at expiry is worth a hair less than a dollar today — but on contracts that resolve in weeks at today's rates the discount rounds away:

$$ \text{price}_{\text{today}} \;=\; e^{-r\,\tau}\, \big(\$1 \cdot p\big) \;\approx\; \$1 \cdot p \quad\text{for small } r\,\tau $$

Here $r$ is the interest rate and $\tau$ the time to expiry. Keep the discount factor in your back pocket; for the rest of this piece I'll quote the clean version, price $=p$.

Why you can't get stiffed

Here is where an event contract stops resembling a casino bet and starts resembling a cleared derivative. When you place a bet with a bookmaker, you are extending the house credit: you hand over your stake, and you are trusting that if you win, the other side is good for the money. On a regulated event-contract exchange, nobody trusts anybody. Both sides post the full value of the contract up front.

Work the arithmetic on a single $1 contract. The YES buyer who pays 62¢ and the NO buyer who pays 38¢ are, between them, funding the entire dollar that will be paid out. The two stakes sum to exactly the maximum the contract can ever owe:

$$ \underbrace{\$0.62}_{\text{YES pays}} \;+\; \underbrace{\$0.38}_{\text{NO pays}} \;=\; \$1 \;=\; \text{the full payout} $$

The exchange escrows that dollar — holds it in a segregated account — and at expiry it cash-settles: the side that was right collects the whole $1, the side that was wrong collects nothing, and the books are square to the penny.³ Four consequences fall straight out of that one design choice, and together they are the financial difference between this and a wager:

Fully collateralized. Every dollar of potential payout is already sitting in escrow before expiry. The money to pay the winner isn't promised; it's posted.
Defined maximum loss. The most you can lose is what you paid — 62¢ on a 62¢ contract. The payoff is bounded at both ends, $0 and $1, so your downside is known before you enter.
No leverage. You can't lose more than you put in, because you funded your whole side of the dollar. There is no margin call, no liquidation cascade, no owing the house money you never had.
No counterparty credit risk. You are not relying on the person on the other side to be solvent. Their stake is already in the pot. The exchange is a custodian of collateral, not a bookmaker taking the other side of your bet.

Fig 2 — both sides fund the dollar; the exchange escrows it and pays the winner

The atomic unit is composable

The reason finance bothers to name a primitive is that you build with it. A single binary is the atom; structured payoffs are molecules. The cleanest example is a range.

Suppose you don't want to bet that inflation comes in above 3% — you want to bet it lands between 3% and 4%. There's no special instrument for that. You just hold the difference of two threshold binaries: long the "above 3%" contract, short the "above 4%" contract. You collect $1 only in the band where the first pays and the second doesn't — that is, exactly when the outcome falls in $[3\%, 4\%)$. In symbols, a digital spread is the difference of two steps:

$$ \underbrace{\mathbf{1}[\,x \ge a\,]}_{\text{above } a} \;-\; \underbrace{\mathbf{1}[\,x \ge b\,]}_{\text{above } b} \;=\; \mathbf{1}[\,a \le x < b\,] \qquad (a < b) $$

Two cliffs, subtracted, make a plateau: a payoff that is $1 inside the band and $0 outside it. Stack enough adjacent binaries and you can approximate any payoff shape you like over the outcome — the binaries are the pixels, and a structured position is the picture you draw with them. This is why an exchange that lists a clean strip of threshold contracts is quietly handing traders a construction kit, not just a menu of bets.

Why the word "derivative" carries the weight

None of this is pedantry about taxonomy. Calling an event contract a derivative is the move that decides who regulates it — and that is the whole ballgame for this category.

Futures and options are derivatives, and in the United States derivatives are the jurisdiction of one agency: the Commodity Futures Trading Commission. Because an event contract is structurally a binary option on a future fact, it falls under the CFTC's authority over derivatives, and a venue that lists them does so as a CFTC-regulated designated contract market — the same license category as a futures exchange.⁴ Kalshi was the first to win that designation. When the CFTC recognized event contracts as a regulated asset class in 2020, what it really did was confirm that this corner of the derivatives world was open for licensed business.⁵

That single classification is why the category looks the way it does today. A regulated, fully-collateralized derivative is an instrument that institutions can touch — which is the backdrop to the numbers that opened this series: monthly volume across the leading venues climbing from under $100M in early 2024 to past $13B by the end of 2025, the owner of the New York Stock Exchange committing up to $2B to distribute one venue's market data, and the odds now read out on CNN and CNBC next to the polls.⁶ You don't get there as a betting product. You get there as an asset class. How the 2020 decision rewrote the rules is its own story, and it's the one I'll tell in Part 11.

What's hard: the binary option has a rap sheet

I owe you the uncomfortable half of this. "Binary option" is a phrase with a genuinely bad reputation, and pretending otherwise would be dishonest.

For years, offshore websites sold things they called binary options to retail customers, and many were close to outright fraud: unlicensed platforms, payouts rigged so the house won regardless, software that quietly moved the expiry against you, and customer funds that vanished when you tried to withdraw. Regulators on several continents warned about them and, in places, banned their sale to retail entirely.⁷ If your instinct on hearing "binary option" is to keep one hand on your wallet, that instinct was earned.

So the distinction has to be drawn precisely, because it is the entire point. The scam was never the instrument — a digital option is just a step-function payoff, a neutral piece of math. The scam was the venue: unregulated, uncollateralized, and self-resolving, where an opaque counterparty both set the terms and decided who won. The regulated version inverts every one of those failures. It is collateralized, so the money to pay you is already escrowed. It is exchange-listed under the CFTC, so a regulator stands behind the venue and customer funds are segregated. And it is transparently resolved against a settlement source named in the rulebook before the market opens, so no one gets to decide the answer after the fact — the subject of Part 7.

Same payoff diagram; opposite trust model. That gap — between a rigged payout offshore and a collateralized, surveilled, rule-bound contract on a licensed exchange — is exactly the gap a license exists to certify. It's the reason I keep returning to the license in this work: at Seeker, the live MVP and demo are how we show the mechanism, but the license is the goal, because the license is what turns "trust us" into "trust the regulator standing behind us." The math was never the hard part. The trust was.

Strip away the politics and the sports — which, honestly, are still where most of the volume lives today⁸ — and what's left is unglamorous and a little reassuring: a binary option, fully funded on both sides, settled against a fact. A derivative. We've known how to price these, collateralize them, and clear them for a very long time. The only new thing is what they're written on — the future itself.

Notes

A binary option (equivalently digital option or all-or-nothing option) pays a fixed amount if the underlying satisfies a condition at expiry and zero otherwise — in contrast to a vanilla option, whose payoff scales continuously with how far the underlying moves past the strike. Standard treatment in any derivatives text, e.g. John C. Hull, Options, Futures, and Other Derivatives (exotic options chapter).
Risk-neutral valuation prices a derivative as the discounted expected payoff under the risk-neutral measure — the probabilities implied by traded prices rather than subjective beliefs. For a cash-or-nothing binary paying $Q$, the value is $e^{-r\tau} Q \cdot \mathbb{P}^{\!*}(\text{event})$; with $Q=\$1$ this is the discounted risk-neutral probability. Real-world and risk-neutral probabilities diverge only to the extent the payoff carries priced, non-diversifiable risk — negligible for most small event contracts. See Hull (risk-neutral valuation) and Cox–Ross (1976).
On a CFTC-regulated designated contract market such as Kalshi, both sides of a binary contract are fully collateralized at the maximum payout: a matched YES/NO pair posts a combined $1 per contract, the exchange holds the collateral in segregated customer accounts, and positions cash-settle at $1 (winner) or $0 (loser) against the contract's specified resolution source. Full collateralization is what removes leverage and counterparty credit risk — the loss is bounded by the premium paid. See Kalshi's rulebook and CFTC requirements for segregated customer funds.
A designated contract market (DCM) is a CFTC-licensed exchange permitted to list futures, options, and event contracts (swaps) to all participants, subject to core principles including financial integrity, customer-fund segregation, and trade surveillance. See the Commodity Exchange Act and 17 CFR Part 38.
Event contracts fall under the CFTC's jurisdiction over derivatives because they are structurally options/swaps written on a future outcome; the 2020 recognition of them as a regulated asset class established the path for licensed, exchange-listed event-contract trading in the U.S. The deeper history of that decision is the subject of Part 11 of this series.
On the category's trajectory: combined monthly volume across leading venues rose from under $100M in early 2024 to past $13B by the end of 2025 (Pew; The Block). Intercontinental Exchange (owner of the NYSE) committed up to $2B to Polymarket to distribute its event-market data (announced October 2025). CNN and CNBC signed deals in December 2025 to carry a prediction market's implied odds on air.
On the offshore retail-binary-options problem: securities and conduct regulators across multiple jurisdictions documented widespread fraud — manipulated payouts and price feeds, refusal to honor withdrawals, and unlicensed operators — and several restricted or banned the sale of binary options to retail investors. See public investor alerts from bodies such as the U.S. SEC/CFTC and the EU's ESMA. The abuses were a function of unregulated, self-dealing venues, not of the instrument's payoff structure.
Sports contracts have made up roughly 80% of leading-venue volume since launching in mid-2024 (The Block). The financial anatomy in this piece is identical whether the underlying fact is an election, a rate decision, or a game — but it would be dishonest to describe the category today as pure forecasting infrastructure. The mechanism is a derivative; what most people trade on it, for now, is sports.