{"slug":"the-september-effect","qid":"septembers_by_year","label":"septembers_by_year","post_title":"the-september-effect","post_url":"/blog/the-september-effect#q-septembers_by_year","columns":["year","sep_return_pct"],"rows":[{"year":2004,"sep_return_pct":0.59},{"year":2005,"sep_return_pct":0.38},{"year":2006,"sep_return_pct":2.25},{"year":2007,"sep_return_pct":3.38},{"year":2008,"sep_return_pct":-9.94},{"year":2009,"sep_return_pct":3.05},{"year":2010,"sep_return_pct":8.38},{"year":2011,"sep_return_pct":-7.42},{"year":2012,"sep_return_pct":1.99},{"year":2013,"sep_return_pct":2.66},{"year":2014,"sep_return_pct":-1.84},{"year":2015,"sep_return_pct":-3.06},{"year":2016,"sep_return_pct":-0.5},{"year":2017,"sep_return_pct":1.51},{"year":2018,"sep_return_pct":0.14},{"year":2019,"sep_return_pct":1.48},{"year":2020,"sep_return_pct":-4.13},{"year":2021,"sep_return_pct":-4.97},{"year":2022,"sep_return_pct":-9.62},{"year":2023,"sep_return_pct":-5.08},{"year":2024,"sep_return_pct":1.79},{"year":2025,"sep_return_pct":3.28}],"shape":"ranking","sql":"WITH month_ends AS\n(\n    SELECT\n        toStartOfMonth(date)           AS month_start,\n        argMax(toFloat64(close), date) AS month_end_close\n    FROM global_markets.stocks_daily_aggs\n    WHERE ticker = 'SPY'\n      AND date < toStartOfYear(today())\n    GROUP BY month_start\n),\nmonthly_returns AS\n(\n    SELECT\n        month_start,\n        month_end_close,\n        lagInFrame(month_end_close, 1) OVER (ORDER BY month_start ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS prev_close\n    FROM month_ends\n)\nSELECT\n    toYear(month_start)                                AS year,\n    round((month_end_close / prev_close - 1) * 100, 2) AS sep_return_pct\nFROM monthly_returns\nWHERE prev_close > 0\n  AND toMonth(month_start) = 9\nORDER BY year","computed_at":"2026-09-18T15:57:51.569843+00:00","elapsed":0.051235103}