S&P 500 (SPX) Up or Down on September 11?
The move lacks solid trading support — treat the new probability with caution.
The pricing has weak support: healthy trading volume and market depth, a tight spread. The probability moved another 5.5 points in the past hour — the market is still repricing.
How credible was the move?
Three separate questions — a move can be genuine while the latest price is still settling. Methodology →
Move validity
Is the move backed by real trading and depth?
WeakThe pricing has weak support: healthy trading volume and market depth, a tight spread.
Consensus stability
Has the market settled at the new probability?
UnsettledThe probability moved another 5.5 points in the past hour — the market is still repricing.
Contract clarity
Will the rules resolve without ambiguity?
HighThe resolution rules are relatively specific, with a named source and a defined deadline.
From the latest trade tape (most recent 200 prints) — a live activity sample, not a lifetime total.
What this market actually measures
This market will resolve to "Up" if the official S&P 500 Index closing price for S&P 500 (SPX) on Friday, September 11, 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, September 11, 2026 is lower than the official S&P 500 Index closing price for SPX on …
This summary shows the opening of the venue's official rules. ProbCast has not yet generated an independent plain-English interpretation for this contract — review the full rules before relying on it.
View full official resolution rules
This market will resolve to "Up" if the official S&P 500 Index closing price for S&P 500 (SPX) on Friday, September 11, 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, September 11, 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
Resolution source: wsj.com
Why the odds moved
The probability rose 6.5 percentage points over the last 24 hours (64.0% → 70.5%).
No verified catalyst has been linked to this move yet. ProbCast does not attribute moves to news without evidence connecting the timing of a specific report to the repricing.
What could move this market next?
- The market's deadline arrivesSeptember 11, 2026 at 4:00 PM ET
The contract must resolve based on what has happened by this date.
- Confirmation at the resolution source (wsj.com)
The rules name this source as the basis for settlement.
Derived from the contract's own mechanics as of Sep 11, 2:26 AM ET. ProbCast does not list scheduled meetings, announcements, or data releases it cannot verify.
Advanced analysis (experimental)
Research signals — these models are still accumulating the history needed for full validation, and they can disagree with the headline read. Model confidence: low · expected error ±29 pts.
What's happening
The price is actively repricing on real volume. The number is still moving — don't treat the latest print as settled consensus yet.
- Probability moved 6.5 pts in ≤6h on adequate liquidity
- Flow one-directional across 80 participants (broad, not a single order)
Read the latest price with caution; conditions make it an unreliable summary right now.
More details — reliability score, dynamics, durability
- Thin-liquidity spike74%
- Choppy / mean-reverting20%
- Trend continuation3%
Short-term motion of the price line (~1h), distinct from the environment above — not a prediction of the final outcome.
Secondary read: leaning toward Trending.
A read-only classification of the market environment — how much weight the current price deserves as a read of consensus. It describes conditions, never a trade.
Market data
24h volume
$64.5K
Liquidity
$12.2K
Total volume
$0
- Category
- Macro / Fed
- Venue
- Polymarket
- Open interest
- —
- Spread
- 1.0 pts
- Best bid
- 70.0%
- Best ask
- 71.0%
- 7-day range
- 64.0% – 71.5%
- Resolves
- Sep 11, 2026
- Resolution
- wsj.com