SPY Opens Up or Down on September 21?

According to the latest prediction market data for the query “SPY Opens Up or Down on September 21?”, traders have formed a strong consensus.

Currently, Up is dominating the market with an overwhelming 5,000% chance of winning. Down follows in second place at 5,000%. The betting volume for this specific market has already reached —, reflecting intense industry interest.

To better assess where each potential outcome stands, the market can be segmented into three distinct trading tiers based on implied probability and contract pricing:

🥇 Tier 1: The Dominant Leader

• Up (5,000%): Currently commanding the highest probability, Up is heavily favored by the order book. Traders looking to back this outcome face a “Buy Yes” contract price of 5,000¢, signaling a high degree of market conviction.

🥈 Tier 2: The Primary Challengers

• Down (5,000%): Positioned as the most viable alternative, Down maintains a 5,000% chance of resolving true. Its “Buy Yes” shares currently trade at 5,000¢.

This market will resolve to "Up" if the open price for S&P 500 (SPY) on September 21, 2026 is higher than the closing price for SPY on the most recent prior trading day.

This market will resolve to "Down" if the open price for S&P 500 (SPY) on September 21, 2026 is lower than the closing price for SPY 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 prices are exactly equal, this market will resolve 50-50. Prices will be used exactly as published by Pyth, without rounding.

If S&P 500 (SPY) does not trade at all during the regular session, the market will resolve 50-50.

The open price refers to the Pyth "Open" value of the 1-minute candle corresponding to the first minute of regular trading hours on the primary exchange.

The closing price refers to the Pyth "Close" value of the 1-minute candle corresponding to the final full minute of regular trading hours on the primary exchange (for a standard full session, the candle beginning at 3:59 PM ET; for a shortened session, the candle beginning one minute before the scheduled early close).

If either of the relevant days has no valid Pyth Open/Close value for the 1-minute candle corresponding to the beginning/end of regular trading hours on the primary exchange, the market will use the first/last valid Pyth price achieved during the regular trading hours of the primary exchange as the effective price. If no valid Pyth price exists for that trading day due to a system outage, data failure, or other technical disruption, the official open or closing price (as applicable) published by the primary exchange on which the listed security trades will be used to determine the effective price for that day.

Only prices achieved during the regular trading hours of the primary exchange on which the listed security trades (typically 9:30 AM – 4:00 PM ET) will be considered.

In the event of a stock split, reverse stock split, or similar corporate action affecting the listed security during the listed time frame, this market will resolve based on split-adjusted prices as displayed on Pyth.

The resolution source for this market will be Pyth, specifically the "Open" and "Close" values for the relevant 1-minute candle available at https://pythdata.app/explore/Equity.US.SPY%2FUSD. Historical 1-minute candles may be accessed by appending a Unix timestamp (seconds) to the Pyth chart URL using the "t=" parameter. Any timestamp within the listed market time frame may be used to view the relevant candle data (e.g., https://pythdata.app/explore/Equity.US.SPY%2FUSD?t=1773432000).