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The probability is essentially unchanged over the last 24 hours. No meaningful probability movement was detected over the past 24 hours.
S&P 500 (SPX) Opens Up or Down on August 3? The current Polymarket probability is 100.0%, essentially unchanged 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 ±11 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 open price for S&P 500 (SPX) on August 3 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 open price for S&P 500 (SPX) on August 3 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 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 open/close price published by S&P 500 Index for that shortened session will still be used for resolution. If the previous trading day has 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 Open/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 Quote-driven.
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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