S&P 500 (SPX) Opens Up or Down on July 22?

Platform comparison

Market context

Polymarket’s contract is pricing **Down at 100%** today, so the market is treating a lower SPX open versus the prior session’s close as fully expected on the present order book.[3] For users holding the position on Polygon, the exposure sits in conditional tokens settled in USDC, so the payout still depends on the official opening print at 9:30 a.m. New York time against the last regular-session close, not on intraday direction after the bell.

That zero implied probability is stark, but it sits alongside a tape that has just seen the S&P 500 close materially higher: the index finished Tuesday at 7,509.20 after a 0.9% gain, helped by semiconductors and broader tech strength.[1] In comparable daily-open markets, the gap risk is usually driven by overnight futures, not the prior day’s cash close alone, so a one-sided price can reflect thin liquidity as much as a strong directional view. The latest reported 0DTE framework also put the expected range around 7,445 to 7,515, which leaves room for a gap move if positioning shifts before the open.[4]

For the rest of the session, traders are watching tariff headlines, Middle East rhetoric, and whether the post-close tone in global risk assets holds into the NYSE open.[1][2] The main dependency is the opening auction itself: a late futures swing, a macro release, or another policy headline can still change the comparison between the 22 July open and the prior close even if the market is already settled on one side.[1][2]

Sources: 1 · 2 · 3 · 4

Methodology

This page reviews S&P 500 (SPX) Opens Up or Down on July 22? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to PolyGram, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

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 does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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.