{"slug":"why-spreads-widen-at-the-open","qid":"mu_open_day","label":"MU: median quoted spread by half hour on July 7, 2026 (ET, regular hours)","post_title":"Why Are Spreads Wider at the Open? Real Data","post_url":"/blog/why-spreads-widen-at-the-open#q-mu_open_day","columns":["et_time","median_spread_cents","median_spread_bps","pct_of_widest","dropped_onesided_locked_crossed"],"rows":[{"et_time":"09:30","median_spread_cents":62,"median_spread_bps":6.7,"pct_of_widest":100,"dropped_onesided_locked_crossed":"109"},{"et_time":"10:00","median_spread_cents":45,"median_spread_bps":4.9,"pct_of_widest":72.6,"dropped_onesided_locked_crossed":"349"},{"et_time":"10:30","median_spread_cents":44,"median_spread_bps":4.9,"pct_of_widest":71,"dropped_onesided_locked_crossed":"56"},{"et_time":"11:00","median_spread_cents":45,"median_spread_bps":4.9,"pct_of_widest":72.6,"dropped_onesided_locked_crossed":"30"},{"et_time":"11:30","median_spread_cents":42,"median_spread_bps":4.6,"pct_of_widest":67.7,"dropped_onesided_locked_crossed":"28"},{"et_time":"12:00","median_spread_cents":39,"median_spread_bps":4.2,"pct_of_widest":62.9,"dropped_onesided_locked_crossed":"21"},{"et_time":"12:30","median_spread_cents":41,"median_spread_bps":4.4,"pct_of_widest":66.1,"dropped_onesided_locked_crossed":"17"},{"et_time":"13:00","median_spread_cents":43,"median_spread_bps":4.6,"pct_of_widest":69.4,"dropped_onesided_locked_crossed":"5"},{"et_time":"13:30","median_spread_cents":41,"median_spread_bps":4.4,"pct_of_widest":66.1,"dropped_onesided_locked_crossed":"10"},{"et_time":"14:00","median_spread_cents":42,"median_spread_bps":4.5,"pct_of_widest":67.7,"dropped_onesided_locked_crossed":"12"},{"et_time":"14:30","median_spread_cents":42,"median_spread_bps":4.6,"pct_of_widest":67.7,"dropped_onesided_locked_crossed":"30"},{"et_time":"15:00","median_spread_cents":39,"median_spread_bps":4.3,"pct_of_widest":62.9,"dropped_onesided_locked_crossed":"33"},{"et_time":"15:30","median_spread_cents":38,"median_spread_bps":4.1,"pct_of_widest":61.3,"dropped_onesided_locked_crossed":"41"}],"shape":"series","sql":"SELECT et_time,\n       median_spread_cents,\n       median_spread_bps,\n       round(100 * median_spread_cents / max(median_spread_cents) OVER (), 1) AS pct_of_widest,\n       dropped_onesided_locked_crossed\nFROM (\n    SELECT formatDateTime(toStartOfInterval(toTimeZone(sip_timestamp, 'America/New_York'), INTERVAL 30 MINUTE), '%H:%i') AS et_time,\n           round(quantileExactIf(0.5)(toFloat64(ask_price - bid_price) * 100, bid_price > 0 AND ask_price > bid_price), 1) AS median_spread_cents,\n           round(quantileExactIf(0.5)(toFloat64(ask_price - bid_price) / ((toFloat64(ask_price) + toFloat64(bid_price)) / 2) * 10000, bid_price > 0 AND ask_price > bid_price), 1) AS median_spread_bps,\n           toString(countIf(NOT (bid_price > 0 AND ask_price > bid_price))) AS dropped_onesided_locked_crossed\n    FROM global_markets.cache_stocks_quotes\n    WHERE ticker = 'MU'\n      AND sip_timestamp >= '2026-07-07 13:30:00'\n      AND sip_timestamp < '2026-07-07 20:00:00'\n    GROUP BY et_time\n)\nORDER BY et_time","computed_at":"2026-08-08T04:51:07.364808+00:00","elapsed":0.658618904}