Since 1926, U.S. large-cap stocks have lost an average 0.9% in September, according to data from Morningstar Direct.
September is the only month during that nearly century-long period in which investors experienced an average loss, according to Morningstar. They saw a profit in all other months.
For example, February saw a positive 0.4% return, on average. While that performance is the second-lowest among the 12 months, is still eclipses September’s by 1.3 percentage points. July reigns supreme with an average return of almost 2%.
The monthly weakness also holds true when looking just at more recent periods.
For example, the S&P 500 stock index has lost an average 1.7% in September since 2000 — the worst monthly performance by more than a percentage point, according to FactSet.
Historically, the last two weeks of September are generally the weakest part of the month, said Abby Yoder, U.S. equity strategist at J.P Morgan Private Bank.
“Starting next week is when it would [tend to get] get a little bit more negative, in terms of seasonality,” Yoder said.
Trying to time the market is a losing bet
Alistair Berg | Digitalvision | Getty Images
Investors holding their money in stocks for the long-term shouldn’t bail, Yoder said.
Trying to time the market is almost always a losing bet, according to financial experts. That’s because it’s impossible to know when good and bad days will occur.
For example, the 10 best trading days by percentage gain for the S&P 500 over the past three decades all occurred during recessions, according to a Wells Fargo analysis published earlier this year.
Plus, average large-cap U.S. stock returns were positive in September for half the years since 1926, according to Morningstar. Put another way: They were only negative half of the time.
As an illustration, investors who sold out of the market in September 2010 would have foregone a 9% return that month — the best monthly performer that year, according to Morningstar.
“It’s all just random,” said Edward McQuarrie, a professor emeritus at Santa Clara University who studies historical investment returns. “Stocks are volatile.”
For example, the popular saying “sell in May and go away” would have investors sell out of stocks in May and buy back in November. The thinking: November to April is the best rolling six-month period for stocks.
It’s all just random.
Edward McQuarrie
professor emeritus at Santa Clara University
“History shows this trading theory has flaws,” wrote Fidelity Investments in April. “More often than not, stocks tend to record gains throughout the year, on average. Thus, selling in May generally doesn’t make a lot of sense.”
Since 2000, the S&P 500 saw gains of 1.1% from May to October, on average,over the six-month period, according to FactSet. The stock index gained 4.8% from November to April.
Historical reason for September weakness
There is a historical reason why stocks often fared poorly in September prior to the early 1900s, McQuarrie said.
It ties into 19th century agriculture, banking practices and the scarcity of money, he said.
At the time, New York City had achieved dominance as a powerful banking hub, especially after the Civil War. Deposits flowed to New York from the rest of the country during the year as farmers planted their crops and farmer purchases accumulated in local banks, which couldn’t put the funds to good use locally, McQuarrie said.
New York banks would lend funds to stock speculators to earn a return on those deposits. In the early fall, country banks drew down balances in New York to pay farmers for their crops. Speculators had to sell their stock as New York banks redeemed the loans, leading stock prices to fall, McQuarrie said.
“The banking system was very different,” he said. “It was systematic, almost annual and money always got tight in September.”
September’s losing streak is somewhat more baffling in modern times, experts said.
Investor psychology is perhaps the most significant factor, they said.
“I think there’s an element of these narratives feeding on themselves,” said Yoder of J.P Morgan. “It’s the same concept as a recession narrative begetting a recession. It gets in the psyche.”
There are likely other contributing elements, she said.
For example, mutual funds generally sell stock to lock in profits and losses for tax purposes — so-called “tax loss harvesting” — near the end of the fiscal year, typically around Oct. 31. Funds often start giving capital-gains tax estimates to investors in October.
Mutual funds seem to be “pulling forward” those tax-oriented stock sales into September more often, Yoder said.
I think there’s an element of these narratives feeding on themselves.
Abby Yoder
U.S. equity strategist at J.P Morgan Private Bank
Investor uncertainty around the outcome of the U.S. presidential election in November and next week’s Federal Reserve policy meeting, during which officials are expected to cut interest rates for the first time since the Covid-19 pandemic began, may exacerbate weakness this September, Yoder said.
“Markets don’t like uncertainty,” she said.
But ultimately, “I don’t think anybody has a good explanation for why the pattern continues, other than the psychological one,” McQuarrie said.
In the macroeconomic environment of late July 2026, personal cash management requires an active, structured approach to wealth preservation. With central bank benchmark rates remaining elevated to ensure long-term disinflation, conservative yield-bearing vehicles—such as short-term U.S. Treasury bills, money market funds, and high-yield savings accounts (HYSAs)—continue to offer reliable nominal returns between 4% and 5%. For individual investors, maximizing net returns requires moving beyond passive checking accounts and executing a disciplined cash laddering strategy.
Leaving substantial liquid capital in traditional bank deposits creates an invisible drag on personal net worth due to ongoing inflation. By implementing a tiered liquidity framework, individuals can split emergency cash reserves and short-term capital allocations across rolling maturities. Allocating cash into 4-week, 8-week, and 13-week Treasury bills creates a continuous cycle of maturing liquidity, allowing investors to continuously reinvest capital at prevailing market yields while maintaining immediate access to emergency funds.
Tax efficiency represents a critical dimension of high-yield cash optimization. For high-earning individuals residing in states with substantial local income taxes, direct holdings in short-term U.S. Treasury instruments often deliver superior net post-tax yields compared to standard commercial bank HYSAs. Because interest earned on federal Treasury bills is strictly exempt from state and local taxation, investors can retain a larger portion of their compounding interest gains without taking on additional credit or market risk.
Ultimately, personal wealth accumulation in mid-2026 relies on intentional capital deployment. Cash should be managed as a productive asset class that generates consistent, risk-free returns. Regularly auditing account yield terms, automating recurring transfers, and leveraging tax-advantaged fixed-income instruments ensures that personal liquidity remains fully optimized against macroeconomic fluctuations.
The personal finance industry in July 2026 is experiencing a technological evolution, driven by the wide deployment of next-generation algorithmic wealth management tools. Modern digital financial platforms have expanded far beyond basic automated index investing; today’s robo-advisors utilize real-time tax-loss harvesting, dynamic portfolio rebalancing, and hyper-personalized spending analysis to optimize retail investor outcomes. However, as these digital solutions become ubiquitous, investors face the crucial challenge of balancing automated execution with human strategic judgment.
The core advantage of automated financial planning platforms lies in their ability to remove emotional bias from investment execution. During periods of market volatility or localized sector realignments, automated algorithms systematically rebalance portfolios back to target asset allocations without falling victim to panic selling or speculative enthusiasm. Furthermore, integrated cash-flow monitoring algorithms analyze individual spending patterns in real time, automatically sweeping surplus income into designated retirement or debt-liquidation accounts to accelerate net worth accumulation.
Despite these operational advantages, algorithmic tools have inherent structural limitations when addressing complex, highly personalized financial life events. Decisions involving multi-generational estate planning, highly complex tax strategies, small business exits, or nuanced real estate transactions require contextual human judgment that software models cannot replicate. Relying solely on automated models without periodic human professional review can result in misaligned risk profiles or overlooked tax liabilities during major life transitions.
The optimal approach for personal financial planning in late 2026 is a hybrid advisory model. Individuals should utilize automated platforms for routine asset allocation, continuous tax optimization, and low-cost passive index tracking, while engaging qualified human financial advisors for periodic strategic planning, estate structuring, and qualitative risk evaluations. This dual approach ensures maximum cost efficiency and disciplined execution while retaining essential strategic guidance.
In the financial environment of mid-2026, personal cash management has re-emerged as a vital component of holistic wealth building. With central bank policy rates holding firm to maintain long-term price stability, yield-bearing instruments such as money market funds, high-yield savings accounts (HYSAs), and short-term Treasury bills continue to offer compounding returns around 4% to 5%. For individual investors, effectively structuring cash reserves requires shifting away from passive bank deposits toward active yield optimization.
A frequent pitfall in personal asset management is leaving substantial liquid capital in traditional checking or low-yield savings accounts, where real returns are continuously eroded by baseline inflation. By implementing a disciplined ‘cash ladder’ strategy—allocating liquid funds across tiered maturities using ultra-short Treasury instruments and FDIC-insured high-yield accounts—individuals can secure maximal yields while retaining immediate liquidity for emergency expenses or tactical investment opportunities.
Simultaneously, investors must evaluate the tax efficiency of their cash holdings based on their tax bracket and geographic location. For high earners situated in states with high local income taxes, direct holdings in short-term U.S. Treasury bills often yield a higher net post-tax return than standard high-yield savings accounts, as Treasury interest is strictly exempt from state and local taxation. Understanding these nuanced tax distinctions allows individuals to capture significant incremental gains without taking on additional market risk.
Ultimately, personal financial health in late 2026 hinges on intentional liquidity management. Cash reserves should not be viewed merely as static emergency funds, but as a dynamic asset class that contributes positively to net worth growth. Regularly auditing yield terms, automating cash transfers, and optimizing for post-tax efficiency ensures that personal capital remains fully productive across all economic conditions.