So Why Don’t You Own It?

Portfolio managers should always have good explanations for their underweight positions. These days, it matters more than ever.

Equity portfolio managers love to talk about the stocks they own. But they don’t usually talk as much about the stocks that they don’t own. In highly concentrated markets, where a small group of huge stocks is driving returns, having conviction in underweight positions is essential.

Underweights always affect a portfolio’s relative returns versus a benchmark. For years, however, portfolio managers weren’t really pressed to explain why they don’t own certain companies. In diversified market environments, underweights just didn’t matter as much to relative performance.

Underweights Can Hurt in Concentrated Markets

That’s changed in recent years. First came the so-called FAANG stocks, then the Magnificent Seven. The latter group—Alphabet, Amazon, Apple, Meta Platforms, Microsoft, NVIDIA and Tesla—comprised a combined 31.1% of the S&P 500 and 21.6% of the MSCI World Index as of August 16. They’ve also driven market returns disproportionately since late 2022. While returns within the group have diverged recently, active managers who didn’t hold at least benchmark weights across the seven megacaps had an inherent disadvantage over the last two years. The predicted total risk contribution of these seven stocks to the S&P 500 Index reached 41.8% in August—more than 2.5 times greater than the top seven stocks in 2010 (Display).

stocks with huge benchmark weights

For growth investors, the conundrum is magnified. Technology stocks comprise nearly 50% of the Russell 1000 Growth Index today; technology and communications services companies combined account for more than 60% of that index.

What’s Different This Time?

Market concentration isn’t new. We’ve seen it before in different forms. At the end of the dot-com bubble in March 2000, technology stocks accounted for almost 50% of the Russell 1000 Growth and nearly a third of the S&P 500. Before the global financial crisis in 2008, financials made up about 40% of the MSCI World Value Index.

However, even when considering those episodes, it’s uncommon for such a small cohort of stocks to be such a disproportionately large weight of the index. For example, from September 1989 to July 2024, the 10 largest stocks in the S&P 500 averaged 21.2% of the index, compared to 34.4% today. So in recent decades, equity portfolios didn’t have to worry as much about how large underweights in individual stocks might affect returns.

Not anymore. Gone are the days when a portfolio manager could simply say, I don’t like the stock, so I won’t own it. Today, not owning a megacap like Apple or NVIDIA could create the biggest relative risk position in the portfolio, and as such, requires a commensurate level of conviction.