Diversification is the lifeblood of investing, but investors might not be as diversified as they think. “The combined weight of stocks with a weight of 3% or more in the index is at an all-time high and continues to rise,” Sløk writes. Diversification doesn’t look much better when looking at stocks that make up 2% of the index: Meta Platforms Tesla and Broadcom That’s a lot of tech and tech-adjacent stocks.