In this photo illustration, an application for an online prediction market site is displayed on an electronic device on February 25, 2026, in Chicago, Illinois.
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The growing popularity of combo contracts in the prediction market has led to an increase in volume, even though it only makes up some of the total activity on the platform.
Combo, or several contracts stacked together that only pay if they all win – similar to parlays in traditional Sportsbooks – has exploded in popularity.
Last month, the combo accounted for more than 50% of the notional volume in Kalshi, driven by the start of the NFL season. A lot of mergers are made from the combination of many sports contracts.
While rival Polymarket is working to expand its US exchange this year, the combo is a priority after the official launch of its domestic platform in May. The combo now accounts for nearly 50% of Polymarket US’s daily volume, helped by growth during the NFL season.
a large part of the volume
But while the combo has a lot of volume, it’s not really where most speculators in the prediction market execute their trades. That’s because the Commodity Futures Trading Commission, the federal regulator that oversees the prediction market, requires exchanges to report volume.
Multi-leg contracts “help [Polymarket and Kalshi] claims higher numbers with lower realistic cash output,” said Chris Park, researcher and founder of MSR Decode, a research firm that analyzes predictive market data.
When a trader places a trade in the prediction market, no matter how much money is placed, the platform measures it as $1 of the notional volume. All event contracts have a binary outcome between $0 and $1, and no matter what price a speculator pays to place a trade, one must take the other side of the order and make $1 in total volume.
But the combo can have payouts that are more than $ 1, which means that people can put very little money down, money in some cases, and it will be measured as potentially thousands of dollars in volume thanks to market makers who take the other side of this high payout trade.
CNBC’s analysis of trade in Kalshi on September 27 shows this in practice. In a single contract, the average amount of cash placed on a trade is less than 47 cents. But in the combo contract, the average of each contract is about 9 cents.
Additionally, while the combo accounted for 58% of Kalshi’s trading volume in September, it accounted for less than 13% of the total transactions on the platform, according to data on Dune.
Other than sports, the combo trumps other categories for the volume of ideas in Kalshi, with over 35% of the total volume shown.
The details of how the combo is measured are not always clear to the public, but the impact on the amount of headline volume can make the platform appear faster than it is now.
The popularity of sports event contracts linked to the prediction market has disrupted traditional online sportsbooks – including parent FanDuel Flutter Entertainment, and DraftKings – whose shares have plunged 70% and 45%, respectively, over the past year.
Apples and oranges
But some notes that investors can confuse the number of activities that are not exactly comparable.
“I have spoken to investors who look at the notional numbers and compare them [the] handle in sports betting, and then make that argument. you know, this prediction market is over [the] sports betting scale,” said Ian Moore, an analyst at Bernstein.
A “handle” in the Sportsbook measures the total dollar amount wagered, while the prediction market counts both sides of the trade.
“When the client buys out-of-the-money deep contracts or combos, the prediction market can have a dollar volume anywhere between 20 to 100 times more than Sportsbooks because CFTC Reporting requires one thing and Sportsbooks report activities they are different,” said Rich Jaycobs, an independent advisor for prediction markets seeking regulatory approval from the CFTC. “The same basic bet, the basic idea is the same, but you take a completely different understanding of the activity.”
Kalshi said that notional volume does not exceed activity. “If people are more interested in other measurements, they can look at other metrics,” said spokesman Jack Such.
While notional volume is the standard metric for prediction markets, some have suggested looking at taker volume as a better measurement. It is because “takers” scoop up liquidity from market makers, instead of providing it, and thus can be a yardstick more than where the activities in the exchange.
Polymarket agrees with that approach.
“We are very pleased to see the volume of takers in terms of buying yes in the combo,” said Kyle Gesuelli, the company’s head of revenue and analytics. That measures the trader’s demand for bets where all the combined results turn out to be true. “This is a step forward for us to better understand the underlying activity.”
Disclosure: CNBC and Kalshi have a commercial relationship that includes customer acquisitions and minority investments.