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 prior trading day's close. The crowd-implied probability of an up day stands at 33%, suggesting traders expect a decline with roughly two-to-one odds. This asymmetry reflects either a genuine bearish positioning ahead of the date or a structural imbalance in how traders are pricing daily directional moves on the index.

Historical data on single-day S&P 500 moves shows that roughly 52% of trading days close higher than their predecessor, with the remaining 48% closing lower. The current 33% probability for an up day therefore sits meaningfully below the long-run baseline, indicating either elevated risk-off sentiment or specific event risk priced into the settlement window. August typically sees thinner trading volumes as summer holidays progress, which can amplify intraday volatility and shift the distribution of daily returns. Comparable prediction markets on other major indices during August periods have shown similar compression toward down-day probabilities when macro uncertainty rises.

Traders should monitor earnings releases, any Federal Reserve communications, and labour-market data in the week preceding 10 August. The US jobs report typically arrives on the first Friday of each month; if July employment data releases on 1 August and surprises materially, it could establish momentum into the following Monday. Treasury yield movements and any geopolitical developments will also influence overnight futures positioning. The settlement window closes at 20:00 UTC on the resolution date, allowing for post-market-close confirmation of the official closing price.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

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 Best Prediction Markets. 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 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Best Prediction Markets trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.