TOTAL VOLUME:
$54.4b
24H VOL:
$218,201,443
24H TRANSACTIONS:
527,797,601
OPEN INTEREST:
$1,191,873,651
500,842
Markets across
13,663
events
MATCHED EVENTS:
1,809
PLATFORM COVERAGE:
4
Polymarket:
51%
VS.
Kalshi:
49%
S&P 500 (SPX) Up or Down on April 17?
Volume:
$497,850
Outcome
Chance %
Price
Liquidity
Volume
24h
7d
Open Interest
Ends in
Result
Trade
Description
This market resolves based on whether the S&P 500 (SPX) closing price on Friday, April 17, 2026 is higher ('Up'), lower ('Down'), or equal ('50-50 split') compared to the most recent prior trading day's close. The resolution uses official closing prices from the Wall Street Journal's Historical Prices database, with fallback provisions for shortened sessions, trading halts, or data disruptions.
PredictionHero - Resolution Divergence Alerts (RDA)
Unified Resolution Criteria (Consistent across platforms)
Both Polymarket and Kalshi resolve based on comparing the S&P 500 closing price on April 17, 2026 against the most recent prior trading day, with identical handling of edge cases including equal prices (50-50), no trading (50-50), shortened sessions, and trading halts.
Primary resolution logic:
Wall Street Journal Historical Prices (Close values) at https://www.wsj.com/market-data/stocksCore resolution logic:
- Market resolves UP if the official S&P 500 closing price on April 17, 2026 is higher than the closing price on the most recent prior trading day.
- Market resolves DOWN if the official S&P 500 closing price on April 17, 2026 is lower than the closing price on the most recent prior trading day.
- Market resolves 50-50 if the two closing prices are exactly equal (rounded to nearest cent).
- Market resolves 50-50 if SPX does not trade during the regular session on April 17, 2026.
- If no official closing price exists due to trading halt, system issue, or other disruption, the last valid on-exchange trade price of the regular session is used as the effective closing price.
Edge cases & Clarifications:
- Prior Trading Day Identification: The most recent prior trading day is ordinarily the previous calendar day, but if that day is a market holiday, the reference date rolls back to the next most recent trading day (e.g., Monday market would reference Friday unless Friday is a holiday, then Thursday).
- Shortened Trading Sessions: If either April 17, 2026 or the prior trading day is a shortened session (e.g., day before Thanksgiving, day after Christmas), the official closing price published by S&P 500 Index for that shortened session is still used for resolution.
- Trading Halt or System Disruption: If either relevant day has no official closing price due to trading halt into market close, system issue, delisting, or other disruption, the last valid on-exchange trade price of the regular session becomes the effective closing price.
- Rounding Convention: All figures are rounded to the nearest cent using standard rounding rules before comparison.
Timing:
Resolution occurs on or after April 17, 2026 market close, once the official S&P 500 closing price is published by the Wall Street Journal and the prior trading day closing price is confirmed.Our PredictionHero Resolution Divergence Alerts (RDA) are there to help users identify potential differences across platforms. They do not replace or supersede the official rules and description of any prediction market. Users are solely responsible for reviewing and understanding the applicable rules and resolution criteria before placing any trade or bet. If you notice a potential inconsistency, discrepancy, or error in an alert, please report it to our team so we can review and improve the accuracy of our data.
Follow the signals, not the noise
Get insights on market conviction, notable shifts, and what the data is quietly signaling.
PredictionHero © 2026 · v0.13.0PredictionHero provides aggregated market data and informational signals only. Nothing on this site constitutes financial, legal, or investment advice. Markets are volatile and speculative. Past performance does not guarantee future results. Always do your own research and consult qualified professionals before making decisions involving risk.