Stop me if you’ve heard this before: The stock market is at record concentration levels. A handful of companies are driving market returns. There’s an AI bubble. FAANG stocks. The Magnificent Seven.

The names change, but the message is familiar. Today, much of the attention is focused on a handful of large technology companies at the center of the AI boom. Their strong performance has made them increasingly influential in the U.S. stock market, and the headlines can make it feel like investors need to do something about it.

The concentration is real. But before reacting to it, an evidence-based investor should step back, put on their Long View lens, and ask a more useful question: What does this actually mean for my portfolio?

The S&P 500 Has Become More Concentrated

Concentration, in investing terms, refers to how much of a portfolio is allocated to a particular stock, sector, country, or other category.

By almost any measure, the S&P 500 is considerably more concentrated today than it was a decade ago:

Data as of June 30, 2026; June 30, 2016 for historical S&P 500.

That matters because concentration makes a portfolio more dependent on a smaller number of outcomes. When a handful of companies represent a large portion of your portfolio, unexpected news that changes the market’s expectations for those companies can have an outsized impact on your results.

But there is an important distinction: the S&P 500 is not your portfolio.

A Global Portfolio Looks Different

Hill Investment Group portfolios aren’t built around the 500 largest companies in a single country. They are built globally, with exposure to more than 14,000 companies across 47 countries.

That changes the picture meaningfully:

Data as of June 30, 2026.

Global diversification naturally reduces the portfolio’s dependence on any single company, sector, or country. The companies driving today’s U.S. market concentration are still there—we own them too—but they represent a smaller portion of the overall portfolio.

Diversification doesn’t mean avoiding the biggest or most successful companies. It means not making your financial future overly dependent on them.

If today’s technology leaders continue to thrive, HIG portfolios participate in that growth. If leadership shifts to different companies, sectors, or countries, we own those too. We don’t need to predict which outcome will occur.

HIG portfolios look much more like the global economy, deviating only when the evidence suggests that doing so can improve expected outcomes for investors.

Built for This Already

Your plan isn’t changing, because it doesn’t need to. Headlines about market concentration can make it feel like investors need to respond to something new. Diversification is one of the oldest ideas in evidence-based investing, and your portfolio has been built for markets like this one since the day we put it together.

Your portfolio includes thousands of companies across developed and emerging markets, large and small, spanning every sector of the global economy. It also leans toward companies with characteristics the evidence associates with higher expected returns: smaller companies, lower relative prices, and stronger profitability.

That structure isn’t designed around today’s headlines. It’s designed for a future we can’t predict.
When one part of the market performs particularly well, the portfolio systematically rebalances rather than allowing yesterday’s winners to dictate tomorrow’s allocation. When market leadership changes, the portfolio already owns the companies positioned to benefit.

That concentration story is real. It’s just about a portfolio built differently than yours.

Markets continue to generate plenty of headlines – from AI and rising stock prices to questions about whether a handful of companies have become too dominant.

In a recent conversation on the Excess Returns podcast, our HIG and Longview Research Partners CIO Matt Zenz discusses how an evidence-based investment process helps investors stay focused on what matters most, without relying on predictions or market timing.

Topics include:

• Should today’s market concentration should concern long-term investors?
• Why do valuations matter, and when do they matter most?
• How thoughtful implementation can improve long-term investment outcomes.
• Why taxable fixed income may be one of the biggest remaining opportunities to improve after-tax returns.

The discussion also explores Longview’s philosophy behind the Longview Advantage ETFs, including EBI and LVIG, and why disciplined implementation can add value over time.

Listen to the full conversation here:
We Asked a $1 Billion Quant Manager Why Concentration Isn’t a Warning — and Small Caps Aren’t Dead.  

Or listen on Spotify or Apple Podcasts.

On June 11th, Space Exploration Technologies, better known as SpaceX (SPCX), began trading on Nasdaq. The headlines were everywhere: A $1.75 trillion valuation. The largest IPO in stock market history. The media is suggesting that this is a once-in-a-generation opportunity.

The noise around IPOs is likely to continue throughout 2026, with more large IPOs planned this year, including OpenAI (known for ChatGPT) and Anthropic (known for Claude.ai).

These companies may change the world as we know it. Maybe not. As investors, we can be excited about these companies, but the evidence tells a clear story about IPOs and how we should treat them in our portfolio.

What the Evidence Shows on IPOs

Based on research from Dimensional Fund Advisors (DFA), we can examine IPO performance across two timeframes: short and medium-term.

Over the short term (first trading day), IPOs typically perform well. This phenomenon is often referred to as the “IPO Pop.” Insiders and some large institutions can buy shares at the IPO price (unavailable to the public) and sell them at higher prices on the open market. Thus, the positive return from the IPO Pop is reserved for insiders and unavailable to the average investor. Individuals can only access shares on the open market meaning after the shares start trading. Often, investors may have to pay higher prices, thereby decreasing (or eliminating) the day-one returns that we see in the data and which the media loves to hype.

After the IPO Pop, over the next six to twelve months after listing, IPOs tend to lag the broader US stock market by 2-3% per year. Please reread the last sentence.

Obviously, these trends may not happen every time. Any individual IPO stock may be different. But the point is that, on average, IPOs tend not to be great investments, particularly when they have high valuations and negative profits, like SpaceX.

An Evidence-Based Alternative

There is good news here. As always, we can leverage this data and evidence to build better portfolios. The funds that we use at HIG typically wait for the IPO hype to fade and for insiders’ lock-up periods to end (increasing the supply of shares) before buying newly listed companies. What does this mean? We expect that, over time, all of our clients will have an appropriate allocation to many of these newly listed companies in the six to twelve-month timeframe as they meet the evidence-based criteria for inclusion in the portfolio.

The Temptation Is Real

We understand the emotional pull. When something feels “historic,” sitting on the sidelines can feel like missing out.

As advisors, our job is to keep clients focused on what the evidence says, not what the moment feels like. The same discipline that keeps you from panic-selling in a downturn is the same discipline that keeps you from buying into a frenzy.

A great company is worth rooting for. It is not always worth buying.

If you’d like to continue this discussion, please reach out to me at ryan@hillinvestmentgroup.com.