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And this month is famous for the well-known market crashes that happened over the course of the past 100 years. In chronological order:
- Wall Street Crash of 1929
- Black Monday of 1987
- October 2008 market sell-off during the Global Financial Crisis
While these events are intensely researched and studied by market and economic historians, financial journalists and bloggers would also write about them when that month of the year comes and accompanied by an implied signal or indication that the markets are going down. With all these goings-on and historical precedents, it is natural for some investors to be fidgety when October comes round the corner.
Statistically, however, October is not as bad as one thought; the worst month, according to the Morningstar article based on the United States (US) market, from 1926 to 2025 was the month before, i.e., September1. Comparing both months for the 100-year period, Octobers returned positive 56 years and negative 44 years, while Septembers lagged at 52 years positive and the rest negative.
This statistic coincidentally brings us to another famous adage found in investing circles: Sell in May and go away. Going back to another statistic presented in the same article, the six-month period between November and April 1926 to 2025 returned an average of 7.67%, as compared to 3.8% for the other half year. While numbers may be on the side of the quote, it is not totally foolproof and guaranteed.
Going back to the topic of the “flavour month” October, we are already seeing impending doom and gloom messaging and happenings all around; rising US bond yields, concerns over a potential artificial intelligence valuation bubble, sharp decline of the local banks’ share prices which caused a pullback on the Straits Times Index, etc.
Investors who are not mentally prepared with these market events may compel themselves to do what instincts tell them: flee and liquidate their positions in panic. This is a very unwise thing to do as it is akin to another phrase heard often: buy high and sell low, and shortchanging one’s own investment portfolio.
No matter which month comes around, the principles remain the same. Stay invested, stay diversified, and manage the portfolio according to one's investment objectives and rebalancing rules, rather than reacting to the calendar or the latest market scare.
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1 – Lefkovitz, Dan. The 10 Best and 10 Worst Months of All Time for the US Stock Market. Morningstar. 7 Oct 2026. https://www.morningstar.com/stocks/10-best-10-worst-months-all-time-us-stock-market#should-you-really-sell-in-may-and-go-away (accessed 16 Oct 2026)






