{"source":"polymarket","id":"1032806","ticker":"spx-opens-up-or-down-on-september-17-2026","slug":"spx-opens-up-or-down-on-september-17-2026","title":"S&P 500 (SPX) Opens Up or Down on September 17?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 17 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 17 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":"2026-09-16T12:01:01Z","end_date":"2026-09-17T20:00:00Z","closed_time":null,"volume":1677.3630959999998,"volume_24hr":1677.3630959999998,"volume_24h_change":null,"normalized_vol_24hr":18.81430435180664,"normalized_volume":12.539636611938477,"liquidity":39682.16989,"open_interest":2387.232864,"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":0.9995,"top_outcome_prob_24h_change":0.38450000000000006,"top_outcome_volume_24h_change":1677.3630959999998,"updated_at":"2026-09-17T14:28:52.441418Z","fetched_at":"2026-09-17T14:28:52.441418Z","added_at":"2026-09-16T12:23:32.082259Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-17-2026","chart_24h":[0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,10.0,20.0,109.027026,109.027026,109.027026,115.277026,126.046257,127.09888900000001,146.038889,156.038889,157.114146,539.425146,1023.655146,1034.145146,1066.472746,1211.162746,1211.162746,1247.516996,1444.537096,1517.673096,1532.673096,1677.3630959999998],"kind":"live","markets":[{"source":"polymarket","id":"4612435","event_id":"1032806","slug":"spx-opens-up-or-down-on-september-17-2026","question":"S&P 500 (SPX) Opens Up or Down on September 17?","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 17 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 17 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":[0.9995,0.0005],"probability":0.9995,"spread":0.001,"active":true,"closed":false,"start_date":"2026-09-16T12:01:01Z","end_date":"2026-09-17T20:00:00Z","closed_time":null,"volume":1677.3630959999998,"volume_24hr":1677.3630959999998,"prob_24h_change":0.38450000000000006,"volume_24h_change":1677.3630959999998,"normalized_vol_24hr":22.115331649780273,"normalized_volume":16.177383422851562,"liquidity":39682.16989,"categories":["Finance"],"countries":[],"updated_at":"2026-09-17T14:28:52.662760Z","fetched_at":"2026-09-17T14:28:52.662760Z","added_at":"2026-09-16T12:23:32.242174Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-17-2026/spx-opens-up-or-down-on-september-17-2026","event_title":"S&P 500 (SPX) Opens Up or Down on September 17?","chart_24h":[0.615,0.605,0.625,0.62,0.62,0.615,0.615,0.625,0.79,0.64,0.76,0.875,0.87,0.905,0.895,0.925,0.91,0.91,0.925,0.97,0.988,0.9775,0.98,0.9835,0.9845,0.9855,0.9905,0.9905,0.9995,0.9995]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/1032806","as_of":"2026-09-17T14:43:44.154365Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on September 17?\" — top market at 100% probability across 1 outcome","source_url":null}}