{"source":"polymarket","id":"1073851","ticker":"spx-opens-up-or-down-on-september-25-2026","slug":"spx-opens-up-or-down-on-september-25-2026","title":"S&P 500 (SPX) Opens Up or Down on September 25?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 25 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 25 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":"2026-09-24T12:01:00Z","end_date":"2026-09-25T20:00:00Z","closed_time":null,"volume":2911.7043240000003,"volume_24hr":2911.704324,"volume_24h_change":null,"normalized_vol_24hr":23.545677185058594,"normalized_volume":14.465215682983398,"liquidity":491.47188,"open_interest":2719.093554,"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":0.9805,"top_outcome_prob_24h_change":0.36050000000000004,"top_outcome_volume_24h_change":2911.704324,"updated_at":"2026-09-25T12:14:47.522501Z","fetched_at":"2026-09-25T12:14:47.522501Z","added_at":"2026-09-24T12:08:00.198444Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-25-2026","chart_24h":[0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,13.888889,47.854405,47.854405,127.854405,127.854405,167.854405,167.854405,167.854405,205.734405,205.734405,205.734405,205.734405,205.734405,246.734405,326.73440500000004,545.314993,761.1949930000001,761.1949930000001,1071.194993,1452.194993,1483.194993,1583.194993,2911.704324],"kind":"live","markets":[{"source":"polymarket","id":"4905773","event_id":"1073851","slug":"spx-opens-up-or-down-on-september-25-2026","question":"S&P 500 (SPX) Opens Up or Down on September 25?","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 25 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 25 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":[0.9805,0.0195],"probability":0.9805,"spread":0.001,"active":true,"closed":false,"start_date":"2026-09-24T12:01:00Z","end_date":"2026-09-25T20:00:00Z","closed_time":null,"volume":2911.7043240000003,"volume_24hr":2911.704324,"prob_24h_change":0.36050000000000004,"volume_24h_change":2911.704324,"normalized_vol_24hr":23.634355545043945,"normalized_volume":18.66851043701172,"liquidity":515.29204,"categories":["Finance"],"countries":[],"updated_at":"2026-09-25T11:54:30.650767Z","fetched_at":"2026-09-25T11:54:30.650767Z","added_at":"2026-09-24T12:08:00.357230Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-25-2026/spx-opens-up-or-down-on-september-25-2026","event_title":"S&P 500 (SPX) Opens Up or Down on September 25?","chart_24h":[0.62,0.625,0.625,0.625,0.615,0.63,0.625,0.605,0.6,0.57,0.57,0.505,0.4,0.4,0.52,0.565,0.565,0.56,0.515,0.52,0.455,0.64,0.65,0.725,0.69,0.76,0.885,0.925,0.94,0.935,0.9805]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/1073851","as_of":"2026-09-25T12:17:26.404678Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on September 25?\" — top market at 98% probability across 1 outcome","source_url":null}}