S&P 500 (SPX) Up or Down on August 10?

Platform comparison

Market context

The S&P 500 will either close higher or lower on Monday, 10 August 2026 compared to the previous trading day's settlement. The crowd is pricing an up move at just 24%, treating a down day as the consensus favourite. That skew reflects the typical pattern of equity indices: single-day reversals are common enough that a coin-flip baseline (50%) gets pulled toward the underdog side by transaction costs, volatility drag, and the psychological weight of recent momentum. Historical data on daily S&P 500 moves shows roughly 51–52% of days close positive in bull markets and 48–49% in bear regimes, meaning the 24% up probability implies either genuine bearish sentiment about early August conditions or a structural mispricing of daily noise.

The week leading into 10 August sits between the US jobs report cycle (typically first Friday of the month) and the mid-August earnings season tail. If the 7 August employment data surprises weak, it could trigger a flight-to-safety selloff that carries into Monday. Conversely, a strong jobs print might lock in gains from the preceding week. The Federal Reserve's communication calendar and any unexpected inflation data from the prior week would also shape positioning. Traders should monitor weekend geopolitical developments and any earnings guidance from late-July releases that might shift sector rotation expectations.

At 24% implied probability for an up day, the market is pricing in roughly a 3-to-1 underdog premium on the bullish outcome. That represents meaningful value if you assess the true daily flip probability as closer to 48–50%, though the exact edge depends on whether late-July momentum and Fed sentiment genuinely warrant a bearish lean or whether the crowd has simply anchored to recent volatility.

Methodology

We track S&P 500 (SPX) Up or Down on August 10? 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 Who Will Win 2026. 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 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.

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.