"S&P 500 (SPX) Opens Up or Down on September 22?" is a daily prediction market on Polymarket where traders buy and sell shares on whether S&P 500's price will finish higher ("Up") or lower ("Down") than its opening price over the daily window specified in the title. The current market probability is 100% for "Up." A price of 100% means the market collectively assigns a 100% chance to that outcome. Prices update in real-time as traders react to live S&P 500 price movements. Shares in the correct outcome are redeemable for $1 each upon market resolution.

"S&P 500 (SPX) Opens Up or Down on September 22?" is an active short-term market on Polymarket. Trading volume can accumulate quickly as the daily window progresses — jump in early to help set the odds before this window closes.

To trade on "S&P 500 (SPX) Opens Up or Down on September 22?," decide whether you believe S&P 500's price at noon ET on September 22 will be higher ("Up") or lower ("Down") than S&P 500's price at noon ET on September 22. Buy "Up" if you think the price will rise day-over-day, or "Down" if you think it will fall. Enter your amount and click "Trade." If your chosen outcome is correct at resolution, each share pays out $1.00. If incorrect, shares are worth $0.

This daily window has closed and resolved. The final outcome was "Up." Use the time-range navigation bar at the top of this page to view adjacent windows or find the current live market.

The "S&P 500 (SPX) Opens Up or Down on September 22?" market resolves based on a comparison of S&P 500's price at noon ET on September 22 versus noon ET on September 22, using Binance SPX-OPENS/USDT 1-minute candle close prices. If the September 22 noon price is higher, the outcome is "Up"; if lower, "Down"; if equal, the market resolves 50-50. You can review the complete resolution criteria and data source in the "Rules" section on this page.

Yes. You don't need to trade to stay informed. Each "S&P 500 (SPX) Opens Up or Down on September 22?" page shows real-time Up/Down probabilities reflecting trader sentiment on whether S&P 500 will be higher or lower at noon ET tomorrow versus today. Use the date navigation features at the top of the page to browse past and upcoming daily windows. You can also view the Order Book and Activity tab for a real-time feed of trade flow.

Polymarket odds are set by real traders putting real money behind their beliefs. “S&P 500 (SPX) Opens Up or Down on September 22?” is still building its trading base for this window, so the current Up/Down probabilities may reflect only a small number of trades. As more participants enter before the window closes, the odds will become increasingly robust. For the latest stats on Polymarket’s overall prediction accuracy, visit the accuracy page on Polymarket.

To place your first trade on "S&P 500 (SPX) Opens Up or Down on September 22?," sign up for a free Polymarket account and fund it using crypto, a credit or debit card, or a bank transfer. Once your account is funded, return to this page — or navigate to the current active daily window using the navigation bar at the top of the page — select "Buy Up" or "Buy Down," enter your amount, and click "Trade." If the window shown in the title has already closed, use the navigation bar to find the current live window. If you're new to prediction markets, click the "How it works" link at the top of any Polymarket page for a quick step-by-step walkthrough.

On Polymarket, the price of each outcome represents the market's implied probability. A price of 100¢ for "Up" in the "S&P 500 (SPX) Opens Up or Down on September 22?" market means traders collectively believe there is roughly a 100% chance that S&P 500's price will finish up over this daily window. If you buy "Up" shares at 100¢ and S&P 500 finishes in that direction, you receive $1.00 per share — a profit of 0¢ per share. If S&P 500 moves the other way, those shares are worth $0. Prices can shift throughout the day as S&P 500's price action unfolds toward the noon ET close.

This daily window closed at Noon ET September 22 and has been resolved. The final outcome was "Up." Use the navigation bar at the top of this page to view adjacent windows or find the current live market.

The "S&P 500 (SPX) Opens Up or Down on September 22?" market has 713 comments where traders share their analysis and react to live S&P 500 price movements. Scroll down to the comments section to read what other participants think. You can also check the "Activity" tab for a real-time feed of trades on this window.

Polymarket is the world's largest prediction market, where you can stay informed and profit from your knowledge of real-world events. Traders buy and sell shares on outcomes for topics ranging from politics and elections to crypto, finance, sports, tech, and culture — including daily S&P 500 direction markets like "S&P 500 (SPX) Opens Up or Down on September 22?." Prices reflect real-time, crowd-sourced probabilities backed by financial conviction, often providing faster and more accurate signals than polls, pundits, or traditional surveys.