US Open, Qualification WTA: Katie Swan vs Mary Stoiana

Platform comparison

Market context

Katie Swan’s US Open qualifying meeting with Mary Stoiana is the kind of late-round match where rankings and recent form matter more than reputation. Stoiana entered as the seed and higher-ranked player, but Swan has already shown the level to beat a seeded opponent in New York qualifying, which helps explain why a market can stay sensitive to even small shifts in live status and completion risk. The crowd-implied 0% YES points to either a settled view that Stoiana’s advance is the base case, or to the market expecting the match outcome to be determined away from a clean pre-match edge.

For traders, the main catalyst is simply whether the scheduled qualifying fixture is completed and who progresses, rather than any broader tennis narrative. The match was listed for Court 11 on 26 August, and recent scoreboards and draw pages indicate the contest either started or has since moved to a completed result, so the key dependency is official completion before the settlement deadline rather than an external announcement. In comparable Grand Slam qualifying markets, the price often turns on draw updates, court scheduling, and whether a match is delayed, suspended or walked over; here, any last-minute retirement, cancellation or unresolved scoreline by 9 September would force the 50-50 fallback.

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Methodology

Political prediction markets differ structurally from sports betting: thinner liquidity, longer settlement windows, higher sensitivity to single news events. This page shows the live Polymarket quote for US Open, Qualification WTA: Katie Swan vs Mary Stoiana plus platform attributes for the three reference venues, so you can see at a glance where the deepest market for this question sits.

Resolution & payout

Political markets typically settle on official candidate or agency confirmation. Polymarket uses UMA Optimistic Oracle: a proposer posts the outcome with a bond, the two-hour window opens, then the smart contract pays USDC.

Kalshi settles USD via CFTC clearinghouse, with clearly defined resolution sources (e.g. AP race calls for elections). Betfair settles after the official outcome is registered with the league or agency. Manifold is play-money.

UK Frequently Asked Questions

What resolution source is used for elections?

Polymarket defines the source per contract — usually Associated Press (AP Race Call), Reuters or the official electoral commission. The source is stated in contract details before the market opens.

Can prediction markets influence election outcomes?

Markets reflect expectations rather than create them. Studies show public-facing markets can anchor expectations, but don't influence the underlying outcome. Political markets are information, not advocacy.

Which platform has the deepest political liquidity?

Polymarket — by far. US 2024 presidential volume was ~$3.5B vs Kalshi (~$200M) and Betfair (~$120M). Where Polymarket is geo-blocked, brokers like Election Predictions UK route into the same order book at 0% fees.

Are political prediction markets legal in my country?

It varies. They sit in legal gray areas in most jurisdictions. Polymarket is geo-blocked from US/UK/EU; some broker frontends have a different geo footprint. Trade only with capital you can afford to lose, and only if you understand the legal status in your jurisdiction.

Are UK election prediction markets available from the UK?

Yes. Betfair Exchange and Smarkets offer UKGC-regulated UK election markets (seat counts, party share, constituency results). Polymarket also lists UK election contracts with deeper global liquidity. Betfair winnings are typically tax-free for UK individuals; Polymarket profits are subject to HMRC CGT.