{"source":"polymarket","id":"848209","ticker":"spx-opens-up-or-down-on-august-17-2026","slug":"spx-opens-up-or-down-on-august-17-2026","title":"S&P 500 (SPX) Opens Up or Down on August 17?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on August 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 August 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":"2026-08-14T12:00:14Z","end_date":"2026-08-17T20:00:00Z","closed_time":null,"volume":4516.899864000001,"volume_24hr":4170.267817000001,"volume_24h_change":null,"normalized_vol_24hr":29.014198303222656,"normalized_volume":16.131576538085938,"liquidity":1452.5754,"open_interest":2640.018026,"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":0.75,"top_outcome_prob_24h_change":0.19499999999999995,"top_outcome_volume_24h_change":3973.766866000001,"updated_at":"2026-08-17T09:01:21.687919Z","fetched_at":"2026-08-17T09:01:21.687919Z","added_at":"2026-08-14T12:16:39.903383Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-august-17-2026","chart_24h":[196.500951,200.667616,197.096189,193.562506,253.562506,253.562506,189.762506,276.429171,306.429171,307.039921,295.285538,295.285538,339.729981,339.729981,371.563313,348.529674,413.529674,418.65967399999994,418.65967399999994,428.65967399999994,438.65967399999994,474.91428799999994,566.2324679999999,869.236274,869.236274,868.583213,915.343775,1251.874602,1691.686525,2789.27892,2784.27892,4170.267817000001],"markets":[{"source":"polymarket","id":"3580733","event_id":"848209","slug":"spx-opens-up-or-down-on-august-17-2026","question":"S&P 500 (SPX) Opens Up or Down on August 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 August 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 August 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":[0.75,0.25],"probability":0.75,"spread":0.06,"active":true,"closed":false,"start_date":"2026-08-14T12:00:14Z","end_date":"2026-08-17T20:00:00Z","closed_time":null,"volume":4516.899864000001,"volume_24hr":4170.267817000001,"prob_24h_change":0.19499999999999995,"volume_24h_change":3973.766866000001,"normalized_vol_24hr":30.07990074157715,"normalized_volume":20.779699325561523,"liquidity":1516.3306,"categories":["Finance"],"countries":[],"updated_at":"2026-08-17T09:06:01.962892Z","fetched_at":"2026-08-17T09:01:22.020516Z","added_at":"2026-08-14T12:16:40.019480Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-august-17-2026/spx-opens-up-or-down-on-august-17-2026","event_title":"S&P 500 (SPX) Opens Up or Down on August 17?","chart_24h":[0.555,0.56,0.555,0.555,0.58,0.58,0.58,0.58,0.58,0.58,0.58,0.575,0.55,0.57,0.565,0.57,0.555,0.555,0.555,0.605,0.645,0.575,0.605,0.64,0.69,0.695,0.685,0.795,0.835,0.775,0.785,0.75]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/848209","as_of":"2026-08-17T09:09:00.603470Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on August 17?\" — top market at 75% probability across 1 outcome","source_url":null}}