TOTAL VOLUME:
$61.9b
24H VOL:
$249,705,498
24H TRANSACTIONS:
600,069,390
OPEN INTEREST:
$1,354,509,605
579,516
Markets across
14,317
events
MATCHED EVENTS:
4,116
PLATFORM COVERAGE:
4
Polymarket:
50%
VS.
Kalshi:
50%
S&P 500 (SPX) Up or Down on April 1? Odds & Prediction Markets
Closed: Apr 1, 4:00 PM EST
Polymarket
Description
This market will resolve to "Up" if the official S&P 500 Index closing price for S&P 500 (SPX) on Wednesday, April 1, 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 Wednesday, April 1, 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
PredictionHero - Resolution Divergence Alerts (RDA)
Divergence Detected
Issue:
Polymarket and Kalshi use fundamentally incompatible resolution frameworks. Polymarket resolves based on directional price movement (Up/Down relative to prior trading day), while Kalshi resolves based on absolute index level thresholds (50 binary Yes/No markets at different price points). These frameworks cannot produce equivalent outcomes.Hero Tip:
Do not assume these markets will resolve identically. On Polymarket, a 0.1% move up resolves YES; on Kalshi, only moves above specific thresholds (5599.9999, 5624.9999, etc.) resolve YES. If SPX closes at 5600 on April 1, Polymarket may resolve YES or NO depending on March 31 close, while Kalshi resolves YES on all 50 markets. Arbitrage risk is extreme.Critical Divergence Points:
Polymarket:
Outlier: Resolves based on directional comparison between April 1 closing price and the most recent prior trading day closing price. Market resolves UP if April 1 close is higher, DOWN if lower, and 50-50 if equal. Key quote: 'This market will resolve to Up if the official S&P 500 Index closing price for S&P 500 (SPX) on Wednesday, April 1, 2026 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day.'Kalshi:
Outlier: Resolves based on 50 separate absolute price-level thresholds. Each market resolves YES if end-of-day SPX on April 1, 2026 exceeds a specific threshold (ranging from 5574.9999 to 7049.9999), and implicitly NO otherwise. Key quote: 'If the end-of-day S&P 500 index value on April 01, 2026 is above 5599.9999, then the market resolves to Yes.'
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