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

Platform comparison

Market context

U.S. equities started August with a clear risk-on tone, and the immediate change over the last 24–48 hours is that de-escalating Middle East tensions have helped lift futures, push crude lower and support the opening bid in the S&P 500. MarketWatch said the S&P 500 rose 1.3% in the latest session and that U.S. stocks opened higher on signs of U.S.-Iran war de-escalation, while the early US cash session on 3 August showed the index up again at the open.[1][8]

That matters for reading the current 100% crowd-implied “Up” price because this market is settled on the cash opening print versus the prior close, not on where the index finishes the day. The prior session ended 30 July at 7,437.63, so the question is whether Monday’s opening auction prints above that level; recent strength into the weekend and the first-trading-day-of-month bounce both point in the same direction, but the move is a narrow open-to-close test rather than a broader trend call.[9][1]

Traders should watch the scheduled U.S. data calendar and any late-breaking geopolitical headlines, because both can move the opening imbalance before 9:30 a.m. ET. August’s first full week includes key releases such as construction spending and the ISM manufacturing index, while earnings from large-cap names like Palantir can still colour futures sentiment and index breadth into the cash open.[15][1]

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 Prediction Today, 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 Prediction Today. 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 Prediction Today 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.