{"source":"polymarket","id":"1063734","ticker":"spx-opens-up-or-down-on-september-23-2026","slug":"spx-opens-up-or-down-on-september-23-2026","title":"S&P 500 (SPX) Opens Up or Down on September 23?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 23 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day.\n\nThis market will resolve to \"Down\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 23 is lower than the official S&P 500 Index closing price for SPX on the most recent prior trading day.\n\nE.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.\n\nIf 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.\n\nIf SPX does not trade at all during the regular session, the market will resolve 50-50.\n\nIf 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.\n\nIf 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.\n\nThe resolution source for this market is the Wall Street Journal, specifically the Open/Close values published by the WSJ under \"Historical Prices\".\n\nUS: https://www.wsj.com/market-data/stocks\nEMEA: https://www.wsj.com/market-data/stocks/emea\nASIA: https://www.wsj.com/market-data/stocks/asia","image":"https://polymarket-upload.s3.us-east-2.amazonaws.com/s-and-p-500-1e40af6979.png","icon":"https://polymarket-upload.s3.us-east-2.amazonaws.com/s-and-p-500-1e40af6979.png","active":true,"closed":false,"start_date":"2026-09-22T12:01:01Z","end_date":"2026-09-23T20:00:00Z","closed_time":null,"volume":2370.0842219999995,"volume_24hr":2370.084222,"volume_24h_change":null,"normalized_vol_24hr":25.295223236083984,"normalized_volume":13.729331016540527,"liquidity":601.5199,"open_interest":2157.658025,"categories":["Finance"],"tags":[{"id":"102683","slug":"spx","label":"SPX"},{"id":"102127","slug":"up-or-down","label":"Up or Down"},{"id":"102281","slug":"daily","label":"Daily"},{"id":"102682","slug":"indicies","label":"Indicies"},{"id":"120","slug":"finance","label":"Finance"},{"id":"102169","slug":"hide-from-new","label":"Hide From New"}],"synthetic":false,"is_group":false,"group_key":null,"parent_event_id":null,"probability":null,"spread":null,"top_outcome":"","top_outcome_probability":0.72,"top_outcome_prob_24h_change":0.21999999999999997,"top_outcome_volume_24h_change":2370.084222,"updated_at":"2026-09-23T07:51:13.132524Z","fetched_at":"2026-09-23T07:51:13.132524Z","added_at":"2026-09-22T12:02:26.571821Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-23-2026","chart_24h":[0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,90.94,181.88,581.88,581.88,593.644706,641.874706,643.660421,664.924384,784.6443840000001,1865.2943839999998,1865.2943839999998,1885.2943839999998,1964.724384,1978.8088899999998,1978.80889,2068.515849,2310.8855869999998],"kind":"live","markets":[{"source":"polymarket","id":"4838134","event_id":"1063734","slug":"spx-opens-up-or-down-on-september-23-2026","question":"S&P 500 (SPX) Opens Up or Down on September 23?","group_item_title":null,"description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 23 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day.\n\nThis market will resolve to \"Down\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 23 is lower than the official S&P 500 Index closing price for SPX on the most recent prior trading day.\n\nE.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.\n\nIf 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.\n\nIf SPX does not trade at all during the regular session, the market will resolve 50-50.\n\nIf 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.\n\nIf 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.\n\nThe resolution source for this market is the Wall Street Journal, specifically the Open/Close values published by the WSJ under \"Historical Prices\".\n\nUS: https://www.wsj.com/market-data/stocks\nEMEA: https://www.wsj.com/market-data/stocks/emea\nASIA: https://www.wsj.com/market-data/stocks/asia","image":"https://polymarket-upload.s3.us-east-2.amazonaws.com/s-and-p-500-1e40af6979.png","icon":"https://polymarket-upload.s3.us-east-2.amazonaws.com/s-and-p-500-1e40af6979.png","outcomes":["Up","Down"],"outcome_prices":[0.72,0.28],"probability":0.72,"spread":0.04,"active":true,"closed":false,"start_date":"2026-09-22T12:01:01Z","end_date":"2026-09-23T20:00:00Z","closed_time":null,"volume":2370.0842219999995,"volume_24hr":2370.084222,"prob_24h_change":0.21999999999999997,"volume_24h_change":2370.084222,"normalized_vol_24hr":25.613683700561523,"normalized_volume":17.71795082092285,"liquidity":888.8248,"categories":["Finance"],"countries":[],"updated_at":"2026-09-23T07:51:13.488383Z","fetched_at":"2026-09-23T07:51:13.488383Z","added_at":"2026-09-22T12:02:26.702615Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-23-2026/spx-opens-up-or-down-on-september-23-2026","event_title":"S&P 500 (SPX) Opens Up or Down on September 23?","chart_24h":[0.5,0.61,0.605,0.6,0.61,0.6,0.61,0.6,0.6,0.53,0.61,0.5,0.4,0.48,0.48,0.52,0.515,0.49,0.515,0.54,0.545,0.625,0.695,0.655,0.68,0.755,0.63]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/1063734","as_of":"2026-09-23T08:04:52.289130Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on September 23?\" — top market at 72% probability across 1 outcome","source_url":null}}