Recent market data indicates a notable shift in the concentration of the S&P 500 index, with the top 10 stocks now accounting for approximately 38% of the index's market capitalization, marking the highest concentration level in 60 years. This surpasses the peak concentration of around 27% observed during the 2000 Dot-Com Bubble. Meanwhile, the next 40 stocks represent only 22.8% of the market cap, the lowest recorded share on record. Concurrently, the ratio of US technology stocks to global technology stocks, as well as to US non-technology stocks, has declined rapidly in recent weeks, raising concerns about a potential tech bubble reminiscent of the early 2000s. Despite these shifts, the overall stock market remains less than 11% below all-time highs, which had previously sparked fears of a tech-like bubble. Market analysts are questioning the applicability of traditional breadth indicators such as the Zweig breadth thrust, given that nearly half of the S&P 500's value is concentrated in just 20 stocks.