{"source":"polymarket","id":"530530","ticker":"spx-opens-up-or-down-on-may-28-2026","slug":"spx-opens-up-or-down-on-may-28-2026","title":"S&P 500 (SPX) Opens Up or Down on May 28?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on May 28 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 May 28 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":"2026-05-27T12:22:51.347356Z","end_date":"2026-05-28T20:00:00Z","closed_time":null,"volume":9117.985886999999,"volume_24hr":9117.985887000003,"volume_24h_change":null,"normalized_vol_24hr":29.00993537902832,"normalized_volume":18.94378662109375,"liquidity":1970.9327,"open_interest":4761.613265,"categories":["Finance"],"tags":[{"id":"102127","slug":"up-or-down","label":"Up or Down"},{"id":"102682","slug":"indicies","label":"Indicies"},{"id":"102169","slug":"hide-from-new","label":"Hide From New"},{"id":"102683","slug":"spx","label":"SPX"},{"id":"102281","slug":"daily","label":"Daily"},{"id":"120","slug":"finance","label":"Finance"},{"id":"104181","slug":"rewards-automation-400-4pt5-50-1","label":"Rewards Automation 400, 4.5, 50 (1)"}],"synthetic":false,"is_group":false,"group_key":null,"parent_event_id":null,"probability":null,"spread":null,"top_outcome":"","top_outcome_probability":0.425,"top_outcome_prob_24h_change":-0.07500000000000001,"top_outcome_volume_24h_change":10876.630071000003,"updated_at":"2026-05-28T06:21:28.149835Z","fetched_at":"2026-05-28T06:21:28.149835Z","added_at":"2026-05-27T12:19:43.224224Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-may-28-2026","chart_24h":[0.0,0.0,0.0,0.0,0.0,0.0,10.0,20.0,20.0,20.0,20.0,20.0,20.0,21.42857,21.42857,21.42857,322.877844,708.409322,884.392047,1472.391331,2879.769482,3477.138687,4678.657582,5746.4140879999995,6774.697185,6907.751232,7650.517394,7650.517394,8474.705887000004,9117.985887000003],"markets":[{"source":"polymarket","id":"2369388","event_id":"530530","slug":"spx-opens-up-or-down-on-may-28-2026","question":"S&P 500 (SPX) Opens Up or Down on May 28?","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 May 28 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 May 28 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":[0.425,0.575],"probability":0.425,"spread":0.01,"active":true,"closed":false,"start_date":"2026-05-27T12:05:06.042612Z","end_date":"2026-05-28T20:00:00Z","closed_time":null,"volume":10876.630070999998,"volume_24hr":10876.630071000003,"prob_24h_change":-0.07500000000000001,"volume_24h_change":10876.630071000003,"normalized_vol_24hr":33.775177001953125,"normalized_volume":25.345266342163086,"liquidity":2718.4046,"categories":["Finance"],"updated_at":"2026-05-28T06:21:59.433023Z","fetched_at":"2026-05-28T06:21:28.161362Z","added_at":"2026-05-27T12:19:43.300172Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-may-28-2026/spx-opens-up-or-down-on-may-28-2026","event_title":"S&P 500 (SPX) Opens Up or Down on May 28?","chart_24h":[0.5,0.5,0.71,0.705,0.66,0.7,0.615,0.635,0.64,0.625,0.615,0.675,0.61,0.605,0.585,0.595,0.54,0.53,0.555,0.635,0.585,0.48,0.335,0.245,0.26,0.255,0.29,0.36,0.355,0.425]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/530530","as_of":"2026-05-28T06:24:21.501508Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on May 28?\" — top market at 42% probability across 1 outcome","source_url":null}}