This market will resolve to "Up" if the official S&P 500 Index open price for S&P 500 (SPX) on October 19 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day.
Current leader
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1 outcome
S&P 500 (SPX) Opens Up or Down on October 19?
Now Gained in 24h Lost in 24hChanges are in percentage points (pp).
Latest update
SurgeMonitoring onlyThe tracked probability rose to 98.75%, up 3.0 percentage points from 95.75% in the latest observation window. No evidence-qualified public source was supplied, so this remains a monitoring note rather than a causal explanation.
Up: 96% → 99%
+3.0 ppStory so far
Recently updatedThe tracked probability rose to 98.75%, up 3.0 percentage points from 95.75% in the latest observation window. No evidence-qualified public source was supplied, so this remains a monitoring note rather than a causal explanation.
A sourced or deterministic market update is available.
Supported by the sources below
What the evidence doesn’t settle
Nothing specific is being tracked yet.
Public sources opened for this story
No public sources are attached yet.
Odds chart
Living timeline
Observed movement
Observed probability rose from 95.75% to 98.75% (+3 percentage points), from 2026-10-19T11:47:32.327Z to 2026-10-19T12:02:56.192Z (UTC).
Editorial research is deferred. This update preserves the observed market change. The cause of the move is not established.
The measured move
Up: 95.75% → 98.75%
Probability moved from 95.75% to 98.75% (+3 percentage points). Observations were 15 minutes 24 seconds apart: 2026-10-19 11:47:32 UTC to 2026-10-19 12:02:56 UTC.
Watch further market observations and reporting about this contract. This update has not been enrolled for editorial research.
No external sources are attached yet.
Observed movement
Observed probability fell from 98% to 94.3% (-3.7 percentage points), from 2026-10-19T08:47:20.274Z to 2026-10-19T09:17:47.482Z (UTC).
Market rules, made readable
Official descriptionRead the rules before reading the headline. Resolution wording decides the outcome, not the news.
This market will resolve to "Up" if the official S&P 500 Index open price for S&P 500 (SPX) on October 19 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 October 19 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".
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Living timeline · 2 significant updates
S&P 500 (SPX) Opens Up or Down on October 19? — probability rises to 98.75%
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