{"_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/1223472","as_of":"2026-10-21T16:10:07.151921Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on October 21?\" — 100% as of 2026-10-21 UTC. https://pdata.world/events/polymarket/1223472","source_url":"https://polymarket.com/event/spx-opens-up-or-down-on-october-21-2026"},"source":"polymarket","id":"1223472","ticker":"spx-opens-up-or-down-on-october-21-2026","slug":"spx-opens-up-or-down-on-october-21-2026","title":"S&P 500 (SPX) Opens Up or Down on October 21?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on October 21 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 21 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":"2026-10-20T12:01:00Z","end_date":"2026-10-21T20:00:00Z","closed_time":null,"volume":8511.654066000001,"volume_24hr":8511.654066000001,"volume_24h_change":null,"normalized_vol_24hr":31.84689712524414,"normalized_volume":18.599733352661133,"liquidity":20345.66972,"open_interest":4716.321949,"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":0.2995000000000001,"top_outcome_volume_24h_change":8511.654066000001,"updated_at":"2026-10-21T15:50:52.725645Z","fetched_at":"2026-10-21T15:50:52.725645Z","added_at":"2026-10-20T12:11:49.918443Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-october-21-2026","chart_24h":[0.0,0.0,0.0,0.0,400.8,400.8,400.8,484.83000000000004,484.83000000000004,494.83000000000004,579.83,579.83,579.83,579.83,579.83,745.002414,745.002414,759.002414,1413.8167,1555.847004,1555.847004,1890.870296,2071.2172050000004,2106.2172050000004,2136.892995,2635.110005,3612.7819,7811.054066000001,7845.054066000001,8511.654066,8511.654066000001],"kind":"live","mutually_exclusive":false,"markets_total":1,"markets":[{"source":"polymarket","id":"5968127","event_id":"1223472","slug":"spx-opens-up-or-down-on-october-21-2026","question":"S&P 500 (SPX) Opens Up or Down on October 21?","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 21 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 21 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":"2026-10-20T12:01:00Z","end_date":"2026-10-21T20:00:00Z","closed_time":null,"result":null,"volume":8511.654066000001,"volume_24hr":8511.654066000001,"prob_24h_change":0.2995000000000001,"volume_24h_change":8511.654066000001,"normalized_vol_24hr":33.20412826538086,"normalized_volume":24.02586555480957,"liquidity":20345.66972,"categories":["Finance"],"countries":[],"updated_at":"2026-10-21T15:50:52.989677Z","fetched_at":"2026-10-21T15:50:52.989677Z","added_at":"2026-10-20T12:11:49.997239Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-october-21-2026/spx-opens-up-or-down-on-october-21-2026","event_title":"S&P 500 (SPX) Opens Up or Down on October 21?","chart_24h":[0.7,0.5,0.515,0.72,0.695,0.675,0.69,0.795,0.72,0.755,0.795,0.8,0.765,0.8,0.75,0.69,0.785,0.76,0.615,0.695,0.7,0.875,0.93,0.9845,0.9995,0.9995,0.9995,0.9995]}]}