What Trillion-Dollar Companies Teach Us About Diversification

Two companies recently crossed a $5 trillion valuation. Let that sink in: five trillion dollars, for a single company.

It’s a headline-grabbing number, and it raises a fair question — how much bigger can these companies actually get, and does it matter to how we invest?

Warren Buffett once said that “size is the anchor of performance,” and there’s real logic to that. At some point, a company gets so large that there simply aren’t enough new markets left to conquer to keep growing at the same pace. History backs this up — today’s largest companies are rarely tomorrow’s largest companies. Leadership at the top of the market rotates more often than people expect.

That’s exactly why we don’t build portfolios around betting on today’s winners staying winners forever — or assuming their run has to end tomorrow either. Both bets require being right about something nobody can consistently predict.

Instead, the approach we use — rooted in decades of academic research from Dimensional Fund Advisors and modern portfolio theory more broadly — is to own a broadly diversified slice of the market across company size, sector, and geography. If today’s giants keep winning, we participate. If leadership shifts to smaller or international companies, as it regularly does, we own those too.

I think of this as a form of financial stewardship: not chasing the hottest headline, but faithfully managing what we’ve been given across a wide enough footprint that we’re not dependent on any single outcome. Proverbs 11:14 reminds us that “in an abundance of counselors there is safety” — and I’d argue there’s a version of that same wisdom in spreading your investments across many companies rather than a concentrated few.

You don’t need to know how big Apple or Nvidia will get in ten years. You just need a portfolio built so that it doesn’t matter.