TOTAL VOLUME:
$54.4b
24H VOL:
$234,875,025
OPEN INTEREST:
$1,205,330,693
501,301
Markets across
13,585
events
MATCHED EVENTS:
1,825
PLATFORM COVERAGE:
4
Polymarket:
51%
VS.
Kalshi:
49%
S&P 500 (SPX) Up or Down on March 20?
Description
This market will resolve to "Up" if the official S&P 500 Index closing price for S&P 500 (SPX) on Friday, March 20, 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 Friday, March 20, 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 resolves on directional price movement (Up/Down vs. prior trading day), while Kalshi resolves on absolute index level thresholds (50 distinct price points). These are fundamentally different settlement mechanisms that will produce divergent outcomes for the same market date.Hero Tip:
If you trade this event, understand which platform you are on: Polymarket bets on whether March 20 closes higher or lower than March 19 (or the most recent prior trading day), while Kalshi bets on whether the index exceeds specific absolute levels. A market that is 'Up' on Polymarket could resolve differently on Kalshi depending on the prior day's close. Arbitrage risk is high if the prior close is near any of Kalshi's 50 thresholds.Critical Divergence Points:
- Polymarket: Outlier: Resolves YES ('Up') if the March 20, 2026 closing price is higher than the most recent prior trading day's close, NO ('Down') if lower, and 50-50 if equal. Uses Wall Street Journal Historical Prices as the resolution source. Key quote: 'This market will resolve to Up if the official S&P 500 Index closing price for S&P 500 (SPX) on Friday, March 20, 2026 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day.'
- Kalshi: Outlier: Resolves YES if the end-of-day S&P 500 index value on March 20, 2026 exceeds any of 50 distinct absolute thresholds (ranging from 5849.9999 to 7324.9999 in 25-point increments). Does not reference prior-day comparison or directional movement. Key quote: 'If the end-of-day S&P 500 index value on March 20, 2026 is above [threshold], then the market resolves to Yes.'
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