The U.S. stock market has surged to unprecedented heights, now accounting for nearly two-thirds of the world’s investable equity market. This dominance, fueled by a decade-long rally in technology stocks—particularly those linked to artificial intelligence—has raised concerns among analysts about the risks of such a concentrated bet.
According to Financial Times, some experts are drawing parallels between the current tech boom and past market bubbles, such as Japan’s late-1980s asset bubble and the early 2000s dot-com crash. The U.S. market’s consistent growth since the 2008 financial crisis has led to skepticism among investors who wonder whether this expansion is sustainable or if a sharp correction is looming.
The “Magnificent Seven” tech giants—Apple, Alphabet, Amazon, Meta, Microsoft, Nvidia, and Tesla—now make up nearly a third of the S&P 500’s $51.8 trillion market value. This level of concentration has led some economists, such as Apollo’s chief economist Torsten Sløk, to warn that the market is in a bubble. Others, however, argue that the rise of AI and strong earnings growth justify these valuations.
Recent market jitters, including concerns over competition from Chinese AI firms and doubts about the sustainability of massive capital expenditures in AI, have slightly pulled U.S. stocks back from their record highs. Some investors are now questioning whether their portfolios, heavily weighted toward the U.S. market, are sufficiently diversified.
While history shows that dominant sectors—like railroads in the early 1900s—eventually cede ground to emerging industries, the question remains whether today’s AI-driven stock boom will follow a similar trajectory or if it signals a long-term shift in global market dynamics.

