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The probability increased by 0.6 percentage points over the last 24 hours. No meaningful probability movement was detected over the past 24 hours.
S&P 500 (SPX) Up or Down on August 3? The current Polymarket probability is 99.8%, up 0.6 percentage points over the last 24 hours. ProbCast classifies this as Stable with medium confidence because the probability has barely moved over the past day.
Research signals — these models are still accumulating the history needed for full validation, and they can disagree with the headline read. Model confidence: high · expected error ±12 pts.
Near resolution or with ambiguous wording, pricing is mechanically thin and can swing on tiny trades. Read end-of-life prices with extra caution.
This market will resolve to "Up" if the official S&P 500 Index closing price for S&P 500 (SPX) on Monday, August 3, 2026 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day. This market will resolve to "Down" if the official S&P 500 Index closing price for S&P 500 (SPX) on Monday, August 3, 2026 is lower than the official S&P 500 Index closing price for SPX on the most recent prior trading day. E.g., ordinarily, a market on Monday would refer to the previous Friday for its most recent closing price, unless that Friday were a market holiday, in which case it would refer to Thursday, or the next most recent trading day. If the two specified closing prices are exactly equal, this market will resolve 50-50. Note that all figures will be rounded to the nearest cent using standard rounding. If SPX does not trade at all during the regular session, the market will resolve 50-50. If either of the relevant days are shortened (for example, due to a market holiday schedule), the official closing price published by S&P 500 Index for that shortened session will still be used for resolution. If either of the relevant days have no official closing price (for example, due to a trading halt into the market close, system issue, delisting, or other disruption), the market will use the last valid on-exchange trade price of the regular session as the effective closing price. The resolution source for this market is the Wall Street Journal, specifically the Close values published by the WSJ under "Historical Prices". US: https://www.wsj.com/market-data/stocks EMEA: https://www.wsj.com/market-data/stocks/emea ASIA: https://www.wsj.com/market-data/stocks/asia
Read with caution —Read the latest price with caution; conditions make it an unreliable summary right now.
Short-term motion of the price line (~1h), distinct from the environment above — not a prediction of the final outcome.
Secondary read: leaning toward Thin market.
A read-only classification of the market environment — how much weight the current price deserves as a read of consensus. It describes conditions, never a trade.
EXPIRING_SOONResolving soonDepth of the order book and volume
Reasonably supported. Generally reliable, with minor caveats. Main caveat: expiring soon.
Low resolution risk, driven mainly by compound question.
How clear the contract wording is — separate from whether the price is trustworthy.
ProbCast provides prediction-market data and analytics for informational purposes only. Not financial, trading, betting, investment, legal, or tax advice. Market-implied probabilities can be wrong, illiquid, manipulated, or affected by ambiguous resolution rules.
ProbCast provides prediction-market data and analytics for informational purposes only. Not financial, trading, betting, investment, legal, or tax advice. ProbCast is not a betting platform, exchange, or broker and does not provide buy or sell recommendations. Intended for users 18+; availability of prediction-market activity varies by jurisdiction. Venue data is aggregated from third parties and may be delayed or inaccurate. See our Terms of Use.
Market-implied probabilities can be wrong, illiquid, manipulated, or affected by ambiguous resolution rules.
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