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S&P 500 (SPX) Opens Up or Down on September 21?
polymarket

S&P 500 (SPX) Opens Up or Down on September 21?

Volume:
$12,085

S&P 500 (SPX) Opens Up or Down on September 21?

 - Polymarket

S&P 500 (SPX) Opens Up or Down on September 21? - Polymarket

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Resolved Sep 21, 2026

Closed: Sep 21, 6:34 PM EST

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S&P 500 (SPX) Opens Up or Down on September 21?

View
100%
31%
Yes 100¢No 0.1¢
0.1¢
N/A
$12,085
N/A
N/A
N/A
Settled
Yes
Total markets: 1

Description

This market will resolve to "Up" if the official S&P 500 Index open price for S&P 500 (SPX) on September 21 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 September 21 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

Polymarket

This market will resolve to "Up" if the official S&P 500 Index open price for S&P 500 (SPX) on September 21 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 September 21 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

Frequently asked questions

On Polymarket, the dashboard for the S&P 500 opening direction market tracks the current odds, price history, and 24-hour trading volume. You can see how traders are pricing the likelihood of the S&P 500 opening up or down on September 21st. Currently, the total volume for this market is $12,085, with $10,733 traded in the last 24 hours. This allows you to gauge market sentiment and track changes in expectations leading up to the open.

Currently, prediction market odds offer a distinct perspective compared to traditional analyst forecasts for the S&P 500’s opening direction. While many analysts are predicting a moderate increase based on recent economic data, this market reflects a more nuanced view, incorporating a wider range of potential outcomes. It’s important to note that prediction markets represent the collective wisdom of traders actively putting capital at risk, which can differ significantly from expert opinions or polls. This provides a real-time assessment of probabilities that may not be captured elsewhere.

On Polymarket, this market is priced through a continuous auction mechanism where traders buy and sell shares representing their belief about the S&P 500’s opening direction. The price of these shares directly reflects the implied probability of each outcome – up or down. On Polymarket, prices reflect that venue's order book, liquidity, and how traders price the outcome right now. The price movements are driven by supply and demand, with increased buying pressure on a particular outcome raising its price and, consequently, its implied probability. This dynamic pricing allows for a constantly updated assessment of market expectations.

This market resolves around Sep 21, 2026, with the outcome confirmed once the event is verifiable from credible public reporting. Specifically, the direction of the S&P 500’s opening price on September 21st will be compared to its closing price on the previous trading day. An increase will settle the “Up” outcome, while a decrease will settle the “Down” outcome. The resolution will be based on widely recognized financial data sources to ensure accuracy and transparency.

Several signals and events could significantly move this market before Sep 21, 2026. Unexpected economic data releases, such as inflation figures or employment reports, could shift investor sentiment. Geopolitical events or major corporate earnings announcements could also introduce volatility. Furthermore, any surprising news regarding Federal Reserve policy or interest rate expectations could heavily influence the perceived likelihood of an S&P 500 increase or decrease. Monitoring these factors will be crucial for understanding potential shifts in this market’s pricing.