{"source":"polymarket","id":"925610","ticker":"spx-opens-up-or-down-on-august-31-2026","slug":"spx-opens-up-or-down-on-august-31-2026","title":"S&P 500 (SPX) Opens Up or Down on August 31?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on August 31 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 August 31 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":"2026-08-28T12:01:04Z","end_date":"2026-08-31T20:00:00Z","closed_time":null,"volume":1378.3586289999998,"volume_24hr":1376.843479,"volume_24h_change":null,"normalized_vol_24hr":21.204071044921875,"normalized_volume":11.895462036132812,"liquidity":405.6349,"open_interest":843.602796,"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":0.14,"top_outcome_prob_24h_change":-0.37,"top_outcome_volume_24h_change":1375.328329,"updated_at":"2026-08-31T02:59:48.673334Z","fetched_at":"2026-08-31T02:59:48.673334Z","added_at":"2026-08-28T12:09:42.968436Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-august-31-2026","chart_24h":[1.51515,1.51515,1.51515,1.51515,1.51515,0.0,0.0,0.0,0.0,0.0,10.0,10.0,10.0,30.0,40.0,40.0,50.0,50.0,50.0,70.0,90.0,100.0,100.0,100.0,110.0,110.0,110.0,655.17,685.17,785.17,805.778107,934.925833,1269.925833,1269.925833,1306.843479,1326.843479],"kind":"live","markets":[{"source":"polymarket","id":"3951266","event_id":"925610","slug":"spx-opens-up-or-down-on-august-31-2026","question":"S&P 500 (SPX) Opens Up or Down on August 31?","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 August 31 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 August 31 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":[0.14,0.86],"probability":0.14,"spread":0.06,"active":true,"closed":false,"start_date":"2026-08-28T12:01:04Z","end_date":"2026-08-31T20:00:00Z","closed_time":null,"volume":1378.3586289999998,"volume_24hr":1376.843479,"prob_24h_change":-0.37,"volume_24h_change":1375.328329,"normalized_vol_24hr":21.461320877075195,"normalized_volume":15.333791732788086,"liquidity":1666.8225,"categories":["Finance"],"countries":[],"updated_at":"2026-08-31T02:59:48.989840Z","fetched_at":"2026-08-31T02:59:48.989840Z","added_at":"2026-08-28T12:09:43.166009Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-august-31-2026/spx-opens-up-or-down-on-august-31-2026","event_title":"S&P 500 (SPX) Opens Up or Down on August 31?","chart_24h":[0.51,0.505,0.505,0.51,0.505,0.51,0.51,0.51,0.51,0.51,0.51,0.51,0.51,0.585,0.625,0.715,0.625,0.485,0.58,0.555,0.225,0.065,0.215,0.185,0.12,0.135]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/925610","as_of":"2026-08-31T03:13:58.972943Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on August 31?\" — top market at 14% probability across 1 outcome","source_url":null}}