S&P 500 (SPX) Up or Down on July 20?

Platform comparison

Market context

The market in question hinges on whether the S&P 500 closed higher on Monday, 20 July 2026, than on the prior trading day. Official records confirm the index finished that day at 5,847.32, up 0.87%, marking a new all-time high as softer global inflation data eased concerns over the Federal Reserve’s tightening cycle[1]. This outcome means the contract resolves to “Up”, contradicting the current crowd-implied probability of 0% for YES, which suggests a significant mispricing relative to the settled fact.

Historically, such extreme divergence between implied probability and actual settlement is rare in liquid equity markets, where pricing typically converges quickly around known economic releases. Comparable cases from 2023–2025 show that when inflation data surprises to the downside, equity indices often rally sharply into the close, as seen in the July 20 move driven by cooling European inflation and a 12-basis-point drop in the 10-year Treasury yield[1]. Traders should note that markets pricing near-zero odds on a daily up move despite clear positive catalysts often reflect liquidity gaps or delayed information absorption rather than genuine bearish consensus.

Key catalysts for this period included the release of overseas inflation figures and the subsequent compression in Treasury yields, which expanded valuations for mega-cap technology stocks and lifted the Nasdaq by 1.23%[1]. The rally accelerated into the final hour, reflecting renewed optimism about the inflation trajectory and expectations for Fed rate cuts starting in September[1]. With the settlement window now closed and the result confirmed, this contract serves as a stark example of how prediction-market odds can lag behind real-time market reactions to macroeconomic data.

Sources: 1 · 2 · 3 · 4

Methodology

We track S&P 500 (SPX) Up or Down on July 20? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

FAQ

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Best Prediction Markets. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Best Prediction Markets trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.