08/03/2026
They say the only free lunch in investing is diversification.
But many investors assume that owning the S&P 500 means they are already properly diversified.
Look beneath the headline, and the picture is more complicated.
Nearly 40% of the index is concentrated in just 10 stocks. Nearly half of that top-10 exposure sits in only three companies: Nvidia, Apple, and Microsoft.
Together, those three companies represent almost one-fifth of the entire S&P 500.
That concentration is not necessarily bad. It has helped drive exceptional market returns. But it does mean that an investment spread across 500 companies may be less diversified than it first appears.
Investors have also experienced a more volatile ride. Earlier in 2026, the S&P 500’s 30-day implied volatility climbed above 23%, nearly double its level at the start of the year. Markets can recover quickly, but sharp swings can return just as fast.
Investors are accepting this concentration and volatility at a time when the S&P 500 is trading at approximately 20.3× forward earnings, while longer-term valuation measures are close to historic extremes.
The S&P 500 can remain an important part of an investment portfolio.
But investors should consider diversification a key ingredient in portfolio construction. That means looking beyond a single index and considering investments with genuinely different sources of return.
Diversification starts where the index ends.
*For informational purposes only. This is not investment advice or a recommendation to purchase or sell any security. Investing involves risk, including the possible loss of capital.
*Sources: S&P 500 constituent weights as of July 20, 2026; Bloomberg volatility data as of March 20, 2026, reported by Penn Mutual Asset Management; FactSet valuation data as of July 17, 2026; Shiller CAPE data as of July 2026. Index weights, volatility, and valuations change over time.
