S&P 500 Concentration: Should the Magnificent Seven Worry You?
By Alpesh Patel OBE, hedge fund manager and author
Short answer: Yes, the S&P 500 is concentrated. A handful of giant technology companies drive most of what the index does. That isn't a reason to panic or sell. The useful question isn't "will the Magnificent Seven fall?".
It's "how much of my money rides on any one company, and could I live with it if that company fell?" If concentration keeps you awake at night, reduce it. Don't try to predict the perfect future.
A viewer put this to me in this week's webinar: they liked the data-driven process, but still worried about how much of the S&P 500 sits in the Magnificent Seven, and about the "circular financing" between AI companies that pays for the boom. It's a fair worry, and a very common one, so here's how I think about it.
Why the S&P 500 is really a handful of companies
The S&P 500 is weighted by market capitalisation, the total value of each company's shares. The bigger the company, the more it counts. When the index's performance is worked out, the giants (Alphabet, Amazon, Microsoft, Apple and Nvidia) do most of the moving. Hundreds of smaller members barely register.
As I put it in the webinar: "So you're really buying a portfolio if you're buying the S&P of seven companies."
That's fine, as long as you like those seven. It also means two things people often miss:
"I own a tracker, so I'm diversified" is only half true. You hold 500 names, but your result depends mainly on a few of them.
It's partly a momentum index. A company's weight grows as its share price rises, so the index automatically holds more of whatever has been going up. That isn't a criticism. It's just worth knowing what you own.
Why "the market is overvalued" is usually the wrong frame
When I lay out the S&P 500 members by how they've done this year, roughly half sit above the index's return and half below. Technology names lead and utilities lag. If the whole market were in a bubble, you'd expect the members to be bunched together, not spread out like that.
My reading of the data: there are pockets of overvaluation in individual shares, but that's not the same as the whole market being overvalued. That's why I look at each company's numbers (value, growth, income, cash flow) rather than reacting to the headline level of the index.
The real answer to concentration worry: regret minimisation
The viewer's concern is partly psychological, and the fix for a psychological problem isn't "be more disciplined". It's to take away the thing causing the worry.
"You're trying to minimise your regret," I said. Think through the four outcomes:
You stay concentrated and it rises: you're happy.
You stay concentrated and it falls: you kick yourself.
You reduce concentration and it rises: you made a bit less, but it still went up and you knew what you were doing.
You reduce concentration and it falls: you fell less, and you'd already acted.
If the second outcome would hurt more than the third, reduce the concentration. Nobody can tell you in advance which outcome you'll get.
Nvidia's "circular financing" in plain English
The circular financing worry is that AI companies are lending each other money to buy each other's products, so the boom is built on IOUs. Here's how I explained it in the webinar.
Imagine Nvidia says to me, "Alpesh, I'm gonna give you five billion dollars to buy Nvidia chips." It sounds as if Nvidia has handed over five billion and is now exposed. In practice the money stays in Nvidia's account, the chips are delivered against it, and if I don't take delivery Nvidia sells the chips to someone else and still pursues me for the debt.
"Money never left Nvidia. Who became indebted? I did."
So the risk sits mainly with the borrower, not the supplier. Where it does matter is a company carrying a lot of debt relative to its size. When I looked at the numbers, that concern applies to Oracle more than to the chip makers. Banks and mortgage lenders do a version of this every day, and it only becomes a crisis in a 2008-style credit event. My conclusion: "Don't get over-concentrated then. It's simple."
How big is too big for one share?
This is the question that actually protects you. The danger isn't failing to call the top. It's waking up to find one company is a huge slice of your money.
A simple structure:
Hold cash for living expenses. At least two years' worth, so you're never a forced seller when markets fall.
Spread the rest across 20 to 40 quality companies. With 40 holdings, each starts at 2.5%.
Look at your weights at least once a year. You don't have to rebalance every time, but you should know what you own.
Set your own ceiling. In the webinar I said that once a single share gets "above twenty percent, I really would start feeling uncomfortable, even as somebody who's relatively risk-loving."
If a winner has grown to 8% or 10% of your portfolio, you probably don't need to do anything. If it's heading past 20%, decide deliberately whether you're comfortable with that.
More shares isn't the same as more diversification
This week's free app, Portfolio Odds, lets you change the number of shares, each share's volatility and how closely they move together (correlation), and shows the range of outcomes for the portfolio as a whole.
Play with it and you'll see two things:
Adding more shares barely changes the picture once you're past about 20. That's why you don't need the hundreds of holdings many funds give you.
Correlation changes it a lot. Shares that don't move in lockstep give a better outcome for the same level of risk. That's the insight Harry Markowitz won a Nobel Prize for, and it's the real reason not to put all your eggs in one basket.
If your 40 shares are really one bet on AI, you're less diversified than the number suggests. Mixing in companies that are driven by different things does more for you than adding a 41st tech stock.
Where should new money go?
When you have new money to invest, or you've taken profits, you have three choices:
Add to winners. You're betting on momentum, and concentration can creep up. Better suited to risk-lovers.
Add to laggards. You're betting on mean reversion. Often sensible, but it can feel like throwing good money after bad.
Rebalance. Top everything back up to equal weights. This is the conventional answer, and there's nothing wrong with it, though watch the tax position outside an ISA or SIPP.
Whichever you choose, the rule is the same: know what you own and how much of it.
Watch the full webinar
In the replay I also cover forward P/E (what you pay for each dollar of future profit), why profits have been rising faster than share prices, the one danger signal I watch for, and viewer questions on SIPP providers and FSCS protection.
Want to see how concentrated your own portfolio is?
Most people don't know how much of their pension rests on a handful of companies, especially when they hold several funds that own the same shares. In our pension reviews we often find the same names repeated across many funds.
Book a call with my team and we'll show you what you actually own.
This article is for education and information only. It is not personal financial advice or a recommendation to buy or sell any investment. The value of investments can fall as well as rise and you may get back less than you invest. Past performance is not a guide to future returns. If you are unsure, seek independent financial advice.
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