{"source":"polymarket","id":"1022462","ticker":"spx-opens-up-or-down-on-september-15-2026","slug":"spx-opens-up-or-down-on-september-15-2026","title":"S&P 500 (SPX) Opens Up or Down on September 15?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 15 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 September 15 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":"2026-09-14T12:01:09Z","end_date":"2026-09-15T20:00:00Z","closed_time":null,"volume":1401.3813999999998,"volume_24hr":1401.3814,"volume_24h_change":null,"normalized_vol_24hr":18.748754501342773,"normalized_volume":11.941667556762695,"liquidity":409.5086,"open_interest":757.914316,"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":0.265,"top_outcome_prob_24h_change":-0.345,"top_outcome_volume_24h_change":1401.3814,"updated_at":"2026-09-15T06:10:30.835605Z","fetched_at":"2026-09-15T06:10:30.835605Z","added_at":"2026-09-14T12:04:18.465847Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-15-2026","chart_24h":[0.0,0.0,15.0,15.0,15.0,15.0,15.0,15.0,15.0,15.0,15.0,15.0,15.0,15.0,236.821261,283.681261,283.681261,448.681261,448.681261,948.681261,1157.1428,1247.1428,1293.206134,1401.3814],"kind":"live","markets":[{"source":"polymarket","id":"4551311","event_id":"1022462","slug":"spx-opens-up-or-down-on-september-15-2026","question":"S&P 500 (SPX) Opens Up or Down on September 15?","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 September 15 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 September 15 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":[0.265,0.735],"probability":0.265,"spread":0.19,"active":true,"closed":false,"start_date":"2026-09-14T12:01:09Z","end_date":"2026-09-15T20:00:00Z","closed_time":null,"volume":1401.3813999999998,"volume_24hr":1401.3814,"prob_24h_change":-0.345,"volume_24h_change":1401.3814,"normalized_vol_24hr":19.62569808959961,"normalized_volume":15.404092788696289,"liquidity":397.3086,"categories":["Finance"],"countries":[],"updated_at":"2026-09-15T06:10:31.091445Z","fetched_at":"2026-09-15T06:10:31.091445Z","added_at":"2026-09-14T12:04:18.696495Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-15-2026/spx-opens-up-or-down-on-september-15-2026","event_title":"S&P 500 (SPX) Opens Up or Down on September 15?","chart_24h":[0.61,0.61,0.615,0.615,0.63,0.625,0.61,0.605,0.6,0.615,0.595,0.595,0.54,0.335,0.525,0.585,0.525,0.505,0.69,0.385,0.235,0.205]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/1022462","as_of":"2026-09-15T06:28:09.703174Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on September 15?\" — top market at 26% probability across 1 outcome","source_url":null}}