{"source":"polymarket","id":"1103155","ticker":"spx-opens-up-or-down-on-september-30-2026","slug":"spx-opens-up-or-down-on-september-30-2026","title":"S&P 500 (SPX) Opens Up or Down on September 30?","description":"This market will resolve to \"Up\" if the official S&P 500 Index open price for S&P 500 (SPX) on September 30 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 30 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":"2026-09-29T12:00:59Z","end_date":"2026-09-30T20:00:00Z","closed_time":null,"volume":7844.023912000001,"volume_24hr":7844.023911999999,"volume_24h_change":null,"normalized_vol_24hr":34.94036865234375,"normalized_volume":18.279041290283203,"liquidity":16786.51801,"open_interest":5619.660151,"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":0.38450000000000006,"top_outcome_volume_24h_change":7844.023911999999,"updated_at":"2026-09-30T17:09:06.984643Z","fetched_at":"2026-09-30T17:09:06.984643Z","added_at":"2026-09-29T19:00:11.563484Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-30-2026","chart_24h":[0.0,219.03679800000003,283.007758,486.597758,949.584758,949.584758,999.584758,1104.944758,1129.944758,1261.974758,1563.93333,2328.665553,3244.445996,7161.293912,7501.703912,7501.703912,7844.023911999999],"kind":"live","markets":[{"source":"polymarket","id":"5122409","event_id":"1103155","slug":"spx-opens-up-or-down-on-september-30-2026","question":"S&P 500 (SPX) Opens Up or Down on September 30?","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 30 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 30 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":"2026-09-29T12:00:59Z","end_date":"2026-09-30T20:00:00Z","closed_time":null,"volume":7844.023912000001,"volume_24hr":7844.023911999999,"prob_24h_change":0.38450000000000006,"volume_24h_change":7844.023911999999,"normalized_vol_24hr":38.136512756347656,"normalized_volume":23.594133377075195,"liquidity":16787.16723,"categories":["Finance"],"countries":[],"updated_at":"2026-09-30T16:17:49.682805Z","fetched_at":"2026-09-30T16:17:49.682805Z","added_at":"2026-09-29T19:00:11.802553Z","url":"https://polymarket.com/event/spx-opens-up-or-down-on-september-30-2026/spx-opens-up-or-down-on-september-30-2026","event_title":"S&P 500 (SPX) Opens Up or Down on September 30?","chart_24h":[0.615,0.625,0.74,0.64,0.68,0.825,0.62,0.635,0.605,0.46,0.47,0.94,0.984,0.9995,0.9995,0.9995,0.9995]}],"_meta":{"attribution":"pdata.world — aggregated prediction-market data across 8 platforms","canonical_url":"https://pdata.world/events/polymarket/1103155","as_of":"2026-09-30T17:09:39.762093Z","docs":"https://api.pdata.world/docs","cite_as":"According to pdata.world (tracking Polymarket): \"S&P 500 (SPX) Opens Up or Down on September 30?\" — top market at 100% probability across 1 outcome","source_url":null}}