{"source":"polymarket","id":"875304","ticker":"spx-opens-up-or-down-on-august-20-2026","slug":"spx-opens-up-or-down-on-august-20-2026","title":"S&P 500 (SPX) Opens Up or Down on August 20?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on August 20 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 20 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":"2026-08-19T12:00:11Z","end_date":"2026-08-20T20:00:00Z","closed_time":null,"volume":3919.97771,"volume_24hr":3919.97771,"volume_24h_change":null,"normalized_vol_24hr":28.933609008789062,"normalized_volume":15.588530540466309,"liquidity":1187.8149,"open_interest":2378.258316,"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":0.59,"top_outcome_prob_24h_change":0.04999999999999993,"top_outcome_volume_24h_change":3966.266574,"updated_at":"2026-08-20T08:02:50.485194Z","fetched_at":"2026-08-20T08:02:50.485194Z","added_at":"2026-08-19T12:54:07.271943Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-august-20-2026","chart_24h":[0.0,0.0,0.0,60.0,60.0,60.0,60.0,60.0,60.0,85.31644700000001,410.026447,515.026447,515.026447,635.026447,755.026447,827.562676,874.975288,2287.408244,2455.463036,2811.330176,2876.190176,3015.415981,3034.858785,3919.97771],"markets":[{"source":"polymarket","id":"3719751","event_id":"875304","slug":"spx-opens-up-or-down-on-august-20-2026","question":"S&P 500 (SPX) Opens Up or Down on August 20?","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 20 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 20 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":[0.59,0.41],"probability":0.59,"spread":0.02,"active":true,"closed":false,"start_date":"2026-08-19T12:00:11Z","end_date":"2026-08-20T20:00:00Z","closed_time":null,"volume":3966.266574,"volume_24hr":3966.266574,"prob_24h_change":0.04999999999999993,"volume_24h_change":3966.266574,"normalized_vol_24hr":30.42133140563965,"normalized_volume":20.142831802368164,"liquidity":1067.7744,"categories":["Finance"],"countries":[],"updated_at":"2026-08-20T08:08:04.014960Z","fetched_at":"2026-08-20T08:02:50.677511Z","added_at":"2026-08-19T12:54:07.435625Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-august-20-2026/spx-opens-up-or-down-on-august-20-2026","event_title":"S&P 500 (SPX) Opens Up or Down on August 20?","chart_24h":[0.54,0.54,0.66,0.67,0.555,0.55,0.665,0.64,0.65,0.65,0.635,0.67,0.66,0.725,0.715,0.615,0.72,0.59]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/875304","as_of":"2026-08-20T08:46:37.736955Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on August 20?\" — top market at 59% probability across 1 outcome","source_url":null}}