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Evaluate Your Allocation to the S&P 500
The Index Is Diversified in Theory. In Reality, Probably Not
Few investment benchmarks are as widely recognized as the S&P 500.
For decades, the S&P 500 has been held up as the gold standard stock index reflecting most of the largest companies in the world. It’s the index that many financial advisors recommend for investment beginners, the benchmark professionals use to measure performance, and the foundation of countless investment strategies. The idea is simple: by owning the 500 largest publicly traded companies in the U.S., you're spreading risk across industries, business models, and economic forces - and participating in their collective growth.
Concentration Has Changed the Equation
While the S&P 500 continues to include 500 different companies, it no longer behaves like a broadly diversified index. Instead, it increasingly reflects the performance of a relatively small group of dominant technology companies whose growth has reshaped the index.
As of early 2026, the top 10 companies in the S&P 500 account for roughly 36-40% of the index value - approximately double the weight of the top ten a decade ago.(6) This level of concentration makes the index behave less like a broad market allocation and more like concentrated exposure to a narrow group of mega-cap companies with similar economic drivers.
Where Selectivity May Add Value
This concentration is neither inherently good nor bad—but it does represent a meaningful shift. When leadership is strong, the index can perform exceptionally well. When it reverses, this concentration can become a headwind.
It's important to clarify that since investing in the index involves owning all 500 companies regardless of valuation, larger investment portfolios(5) may benefit from a more selective approach - evaluating individual security holdings (rather than holding the entire index) and allocating capital to individual securities where relative value and long-term opportunity appear more compelling. This can create are more balanced portfolio based on quality and potential.
Concentration Has Occurred Before in History
Periods of elevated concentration have occurred before—most notably during the “Nifty Fifty” era of the late 1960s and the technology bubble of the late 1990s—both of which were followed by extended periods where broader or more value-oriented segments outperformed by wide margins.(9)
While the S&P 500 index has been a stellar performer for quite a number of years, it is important to consider that it may underperform relative to other investment indexes or customized portfolios that bypass the current risks of this heavily concentrated index. Keep an eye out for transitions when they occur.
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