- Explore the Halloween Effect, a seasonal investing theory linking stronger stock performance to the months between October and May.
- Learn how historical data and global studies support this centuries-old pattern across 36 of 37 major markets.
- Discover whether this market anomaly is investor psychology, coincidence, or a credible seasonal trading strategy.
Forget scary movies — this October, we’re diving into something far more mysterious: the Halloween Effect.
The Halloween Effect is an investing theory suggesting that stocks perform better between October 31st and May 1st — a pattern some investors have followed for centuries. But is it a coincidence, or a credible seasonal advantage?
This article is a journalistic opinion piece which has been written based on independent research. It is intended to inform investors and should not be taken as a recommendation or financial advice.
In this short video, Coreena Robertson explores the origins of this eerie market anomaly, uncovering the history, research, and results behind one of investing’s oldest seasonal theories.
From 17th-century London traders to modern data-backed studies, the Halloween Effect has long intrigued economists. Research published in the American Economic Review found that markets outperformed during the November–April period in 36 out of 37 countries studied, with returns beating the May–October stretch over 80 per cent of the time across five-year periods.
So why does it happen? Some suggest it stems from early investor behaviour — when wealthy traders left cities for summer holidays, lowering market activity until their return in autumn. Others believe it’s a self-fulfilling prophecy, reinforced by generations of investors “selling in May and going away.”
Whether you view it as market magic or statistical quirk, one thing’s certain: the Halloween Effect continues to haunt investment debates every October.
Watch the full video to uncover the facts, the folklore, and the financial data behind this enduring seasonal mystery.
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