{"slug":"the-september-effect","qid":"worst_septembers","label":"worst_septembers","post_title":"the-september-effect","post_url":"/blog/the-september-effect#q-worst_septembers","columns":["label","sep_return_pct"],"rows":[{"label":"Sep 2008","sep_return_pct":-9.94},{"label":"Sep 2022","sep_return_pct":-9.62},{"label":"Sep 2011","sep_return_pct":-7.42}],"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    formatDateTime(month_start, '%b %Y')               AS label,\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 sep_return_pct ASC\nLIMIT 3","computed_at":"2026-09-18T15:57:51.717764+00:00","elapsed":0.054030309}