{"_meta":{"attribution":"Data aggregated by pdata.world (https://pdata.world) from 8 prediction-market venues; CC BY 4.0; source data © each venue.","canonical_url":"https://pdata.world/events/polymarket/1217437","as_of":"2026-10-20T08:59:33.267555Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on October 20?\" — 66% as of 2026-10-20 UTC. https://pdata.world/events/polymarket/1217437","source_url":"https://polymarket.com/event/spx-opens-up-or-down-on-october-20-2026"},"source":"polymarket","id":"1217437","ticker":"spx-opens-up-or-down-on-october-20-2026","slug":"spx-opens-up-or-down-on-october-20-2026","title":"S&P 500 (SPX) Opens Up or Down on October 20?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on October 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 October 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":"2026-10-19T12:00:58Z","end_date":"2026-10-20T20:00:00Z","closed_time":null,"volume":3899.696852,"volume_24hr":3906.5461659999996,"volume_24h_change":null,"normalized_vol_24hr":26.43163299560547,"normalized_volume":15.531314849853516,"liquidity":688.2886,"open_interest":2600.617931,"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":0.665,"top_outcome_prob_24h_change":0.14500000000000002,"top_outcome_volume_24h_change":3982.108617,"updated_at":"2026-10-20T08:40:39.463641Z","fetched_at":"2026-10-20T08:40:39.463641Z","added_at":"2026-10-19T12:21:44.498567Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-october-20-2026","chart_24h":[6.849314,6.849314,6.849314,6.849314,6.849314,6.849314,6.849314,6.849314,6.849314,6.849314,6.849314,6.849314,46.849314,46.849314,46.849314,126.84931399999999,266.849314,266.849314,1120.665442,1616.895442,2221.6486,2721.093045,3385.464826,3754.464826,3801.283008,3906.5461659999996,3906.5461659999996,3906.5461659999996],"kind":"live","mutually_exclusive":false,"markets_total":1,"markets":[{"source":"polymarket","id":"5920650","event_id":"1217437","slug":"spx-opens-up-or-down-on-october-20-2026","question":"S&P 500 (SPX) Opens Up or Down on October 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 October 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 October 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":[0.665,0.335],"probability":0.665,"spread":0.11,"active":true,"closed":false,"start_date":"2026-10-19T12:00:58Z","end_date":"2026-10-20T20:00:00Z","closed_time":null,"result":null,"volume":3899.696852,"volume_24hr":3988.957931,"prob_24h_change":0.14500000000000002,"volume_24h_change":3982.108617,"normalized_vol_24hr":28.628902435302734,"normalized_volume":20.060640335083008,"liquidity":719.3988,"categories":["Finance"],"countries":[],"updated_at":"2026-10-20T08:40:39.682682Z","fetched_at":"2026-10-20T08:40:39.682682Z","added_at":"2026-10-19T12:21:44.579007Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-october-20-2026/spx-opens-up-or-down-on-october-20-2026","event_title":"S&P 500 (SPX) Opens Up or Down on October 20?","chart_24h":[0.52,0.51,0.52,0.525,0.73,0.73,0.735,0.46,0.595,0.43,0.615,0.73,0.645,0.645,0.55,0.52,0.61,0.7,0.55,0.665]}]}