S&P 500 (SPX) Opens Up or Down on August 3?

Platform comparison

Market context

Polymarket is pricing this contract at **100% Yes**, so the market is effectively assuming the S&P 500 will open above the prior session’s close on 3 August. For a Polymarket user, that means the position settles off the official cash index open in USDC on Polygon through conditional tokens, not off intraday futures or the opening print in an ETF, so the final reference point is the exchange-calculated SPX open versus the previous trading day’s close.

That reading is consistent with the backdrop after Friday’s strong finish: the S&P 500 ended 31 July at **7,489.72**, up **0.7%**, with breadth positive but still mixed underneath the surface. Morning commentary ahead of the bell pointed to a modest gap higher in futures, with S&P 500 futures up around **0.5% to 0.6%** and cash indications near **7,527**, which would leave the index opening above Friday’s close if that strength held into the auction.[3][6][9][12]

Traders should watch the **10:00 a.m. ET ISM manufacturing release**, because it can quickly change early risk appetite after the opening print. Reuters-linked pre-market coverage also flagged a drop in Brent crude and lower Treasury yields, both of which tend to support equity index futures and can help preserve an up-open if there is no sharp reversal into the bell.[12] The main dependency for this market is simple: the opening auction has to be above the last cash close, so any late pre-open fade, risk-off headline, or volatility in mega-cap earnings sentiment could still matter more than the overnight futures colour.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews S&P 500 (SPX) Opens Up or Down on August 3? 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

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 PolyGram. 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.

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.