Investors may become enamoured with popular stocks based on recent performance or media attention—and overconcentrate their portfolio holdings in these companies. 

This content will only be shown when vOne example is the rise of the large US technology companies known as the Magnificent 7 (Alphabet, Amazon, Apple, Meta Platforms, Microsoft, NVIDIA, and Tesla). But the chart below shows that many fast-growing stocks have stopped outperforming after becoming one of the 10 largest stocks in the US. On average, companies that outperformed the market on the way up failed to outperform in the years after making the Top 10 list.