Stock market declines in Paris are rare but becoming more frequent

While the CAC 40 traded near its all-time highs in 2023, the French Financial Markets Authority (AMF) examined extreme price fluctuations over the 2013–2023 period.

Although these drops in performance remain rare, their frequency and magnitude have increased, and this phenomenon is also observed in Europe and the United States.
 

Increased Frequency of Sharp Declines in 2023
Alstom plummeted 37.6% on October 5, 2023; Worldline fell 59.2% on October 25 of the same year. More recently, Edenred plunged 13% on July 23, and STMicroelectronics fell 14% two days later. The AMF recorded 9 instances of declines of 10% or more on the CAC 40 in 2023, affecting 7 stocks, compared with only 3 instances in 2022 and 6 in 2021. By comparison, between 2013 and 2017, there were only 1 to 4 similar instances per year. 

These sharp fluctuations were not followed by a return to pre-plunge price levels, even though the liquidity of the securities did not deteriorate: trading volumes and order book depth remained stable.
 

A global trend, not specific to the CAC 40
The increase in significant downward movements is not limited to the Paris market. Similar phenomena have been observed in other European indices and in the United States. This reflects a global dynamic affecting stock markets.
 

Explanatory factors: high valuations and concentration of performance
The AMF has identified several factors that may explain this increase in dropouts:
 

1. High valuation levels: In 2023, estimated price-to-earnings ratios per share were near all-time highs in both France and the United States. As a result, bad news—such as financial results deemed disappointing—was met with a harsher market reaction.
 

2. Concentration of Returns: An increasing share of index gains is generated by a small number of blue-chip stocks. For example, in 2023, 11 stocks in the Stoxx Europe 600 alone accounted for 50% of the index’s gains. This has reinforced the trend among investors to heavily reward top-performing stocks and penalize underperformers, increasing intra-index volatility.
 

Impact of Market Participants
The study also analyzed the role of market participants, including short sellers, asset management firms, and individual investors. However, none of these categories was identified as the primary cause of the market declines.
 

A Phenomenon to Watch
Although rare, the increasing frequency of stock market sell-offs highlights the financial markets’ heightened vulnerability to bad news, against a backdrop of high valuations and concentrated performance. The AMF will continue to monitor these dynamics to better understand their implications for market stability.