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

Platform comparison

Market context

The immediate change in the last 24-48 hours is that US equities finished the prior session firmer, with the S&P 500 closing at 7,489.72 on Friday after a 0.7% gain, and futures were pointing higher again on Monday morning as risk appetite improved on signs of easing geopolitical तनाव and a softer rates backdrop.[1][2] That puts the index into today’s session with a positive overnight tone rather than a defensive one.

The historical read is straightforward: a market already at elevated levels and coming off a strong finish can still move either way on a single day, and August has typically been a relatively muted month for the S&P 500 rather than a clean directional trend.[15] The last close also matters for this market’s binary setup, because the settlement compares Monday’s official close with Friday’s 7,489.72, so even a small reversal from the open would be enough to change the outcome.[1][5][9]

For traders watching the session, the main intraday catalyst is the 9:45 a.m. ET S&P Global US manufacturing PMI final for July, followed by the 10:00 a.m. ET ISM manufacturing print and associated pricing data later in the week.[6] The market is also digesting Friday’s broad earnings-led strength, with large-cap technology and AI-linked names again a key driver of index direction, so further sector leadership or a fade in megacaps will matter more than the headline index level alone.[1][2]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews S&P 500 (SPX) 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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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.

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.

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.