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September has long carried an unfavourable reputation for global equity markets, and European stocks are no exception.

Historical data reveals that the month consistently delivers weak performances for major continental indices, echoing the negative seasonal pattern seen on Wall Street.

Over the past 30 years, the Euro Stoxx 50 index, Europe’s leading blue-chip benchmark, has posted an average September loss of 1.56%, narrowly trailing August’s 1.59% decline, which ranks as the worst month of the year. In 15 of those 30 years, the index closed the month in the red, underscoring a near-coin toss probability of a negative outcome.

The negative seasonality remains intact even when narrowing the lens to the past decade. Since 2014, the Euro Stoxx 50 has recorded an average 1% drop in September, with six out of ten instances ending in losses.

And it’s not just the Euro Stoxx 50 feeling the September slump. The broader Euro Stoxx 600, which captures a wider slice of the market, has also stumbled during this month, with an average loss of 0.96% since its launch in 2002.

That mirrors the S&P 500’s performance, which has lost about 1% on average during the same month over recent decades, the worst return of any month for US equities.

The September seasonal weakness in equity markets may be linked to a confluence of factors: post-summer rebalancing by institutional investors, renewed macroeconomic uncertainty heading into the year-end, and traditionally lower trading volumes following the holiday period.

National indices not spared

Across Europe’s major country indices, the September effect is equally pronounced.

Germany’s DAX index has delivered an average return of -1.62% in September, second only to August in terms of weakness, with a winning rate of just 47%.

France’s CAC 40 fares similarly, averaging a 1.49% decline in September, its poorest month of the year, although it manages a slightly better 53% winning rate.

Italy’s FTSE MIB index, while averaging a flat 0% return in September over the long term, is currently on a streak of four consecutive negative Septembers.

10 European stocks suffer steepest September setbacks

At the individual stock level, several of Europe’s heavyweight names have demonstrated a persistent pattern of September underperformance, with average losses outpacing their monthly norms and, in many cases, marking September as the worst-performing month of the year.

Infineon (Germany): The semiconductor group has an average September loss of 6.13%, its weakest month historically. The stock has closed lower in four consecutive Septembers, with its worst drop of 52.34% occurring in 2001.

Vivendi (France): With a dismal 33% winning rate in September and an average loss of 4.07%, the French media firm experienced a record monthly drop of 66% in 2021.

Airbus (Netherlands/France): The aerospace giant has fallen in six straight Septembers, averaging a 4.01% decline. Its worst September came in 2001, with shares plunging 37.04%.

LVMH (France): Europe’s largest luxury group averages a 3.42% September drop, despite a marginally better 53% win rate. The worst September loss came in 2001, at -34.71%.

Société Générale (France): The French bank posts an average September return of -3.11%, with a 47% win rate. Its most severe drop was -40.38% in 1998.

Schneider Electric (France): The electrical equipment firm has an average September return of -2.16%, with its steepest fall of 34.43% occurring in 2001.

E.ON (Germany): The utility company averages a 2.18% September loss with a 43% winning rate. Its worst drop came in 2015, at -24.03%.

Deutsche Post AG (Germany): The logistics and courier group averages a 1.97% loss in September. It saw its sharpest monthly decline of -22.41% in 2002.

Kering (France): Another luxury player, Kering averages a 1.76% drop in September with a 43% win rate. The worst September came in 2002 (-23.35%), and the stock is currently on a four-year losing streak.

SAP (Germany): Europe’s largest software company averages a 1.6% September decline. A six-year streak of negative Septembers ended in 2024, though the stock once dropped 40.98% in the month back in 2002.