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

Platform comparison

Market context

SPX is effectively being priced as an *up day*, with the crowd-implied probability at 100% YES and spot-market tone already supportive after Friday’s gain and a firmer Monday open. That is notably more bullish than the usual cross-platform split: Polymarket’s own public page shows a separate, differently defined SPX intraday contract at 50/50 for “Up”, so the apparent divergence is mostly a function of contract design rather than a clean disagreement on direction.[18]

The backdrop for reading that certainty is a market that has already rebounded from last week’s post-Fed weakness, with the S&P 500 closing Friday up 0.70% at 7,489.72 and futures higher on Monday as geopolitical risk eased and oil prices fell.[2][1][15] Several desks described the tape as range-bound but improved, with sentiment helped by strong megacap earnings and lower volatility, although breadth remains mixed and some strategists still warn that the rally is narrow rather than broadly confirmed.[5][12][13]

For traders, the main catalysts are today’s US data calendar and any fresh macro or geopolitical headlines. CNBC flagged the final July S&P Global manufacturing PMI, construction spending and the July ISM manufacturing survey for Monday, while the week also builds towards payrolls; these releases matter because they can move Treasury yields, rate-cut expectations and therefore equity futures into the cash close.[6][3][13] Oil and Middle East headlines remain a parallel risk factor, since any reversal in the current de-escalation narrative could quickly alter index sentiment.[1][15]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

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

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 Best Prediction Markets. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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.