What Is the CAPE Ratio — and Is the Stock Market Overvalued?

There's a number that a certain type of finance person checks the way anxious travelers check flight departure boards. It's called the CAPE ratio. And depending on where it sits when you're reading this, it's either quietly confirming your worst suspicions about the stock market or giving bears one more thing to be smug about at dinner parties.

Here's the thing: most people who've heard "the market looks expensive" have never actually been shown the math behind that claim. The CAPE ratio is that math. And once you understand it, you'll never look at a regular P/E ratio the same way again — because the regular version has a flaw big enough to drive a recession through.

What the CAPE Ratio Actually Is

CAPE stands for Cyclically Adjusted Price-to-Earnings ratio. You'll also hear it called the Shiller P/E, named after Yale economist Robert Shiller, who popularized it and won a Nobel Prize in 2013 partly for the underlying work.

Let's back up. You already know what a price-to-earnings ratio is, at least roughly. Price divided by earnings. If a company trades at $100 a share and earns $5 per share, its P/E is 20. You're paying 20 times earnings. The S&P 500 as a whole has a P/E ratio, and when it gets high, the conventional wisdom is that stocks are pricey.

The problem is that "earnings" bounce around wildly. In a recession — when companies are laying people off and writing down losses — earnings collapse. That makes the P/E ratio look artificially sky-high just when stocks are actually at their most attractive buying points. Flip it around: in a boom, earnings surge and the P/E looks deceptively reasonable right before a correction. The standard P/E ratio is, bluntly, a bit of a liar.

Shiller's fix was elegant. Instead of using one year of earnings, take ten. Average out a full decade of earnings, adjust each year for inflation, and then divide the current price by that smoothed figure. What you get is a valuation measure that doesn't panic during recessions or get giddy during booms. It sees through the cycle — hence "cyclically adjusted."

The formula looks like this:

CAPE = Current S&P 500 Price ÷ 10-Year Average Inflation-Adjusted Earnings

That's it. No magic. Just patience built into the denominator.

Why a Single Number Can Tell You So Much

A CAPE ratio of, say, 16 means you're paying $16 for every $1 of ten-year-average earnings the index produces. Historically, that's around fair value. A CAPE of 35 means you're paying more than twice that. You're either expecting explosive future growth, or you're gambling that the next buyer will pay even more than you did — what economists call the greater fool theory, though they use politer language in academic papers.

The long-run average CAPE for the U.S. market sits somewhere around 16–17, depending on how far back you pull the data. Shiller's dataset goes all the way to 1871, which is genuinely wild and also incredibly useful for context.

When CAPE is high, forward returns tend to be lower. When CAPE is low — like in 1982, when it scraped below 7 — the decade that follows tends to be spectacular. This isn't a guarantee. It's a gravity-like force that works over long time horizons and gets messier the shorter your window gets.

Where the CAPE Has Been — and What Happened Next

The table below shows some historically significant CAPE readings and the market's general behavior in the years that followed.

[table:cape-historical-readings]

The standout data point is January 2000, when the CAPE hit 44 — a figure that looked insane at the time and looks even more insane in retrospect. The S&P 500 went on to lose roughly half its value over the next two-plus years. The 2007 peak at around 27 preceded a 57% drawdown in the S&P 500 during the financial crisis.

The 1982 trough — CAPE near 7 — kicked off one of the greatest bull markets in American history. The index roughly tripled over the next five years.

Now, has CAPE been elevated in recent years? Yes, noticeably. The ratio spent a long stretch above 30, and at various points pushed close to or above the levels seen in 2007. Whether that means a crash is imminent is exactly the wrong question to ask — and I'll explain why in a moment.

The Very Loud Criticism of the CAPE Ratio

The CAPE ratio has real critics and they aren't wrong. Here are the main objections, because you deserve the honest version of this.

Accounting rule changes distort the denominator. The way companies report earnings today is different from how they reported earnings in 1950 or even 1990. Post-2001 accounting rule changes (specifically around goodwill write-downs) tend to make earnings look lower in downturns, which inflates CAPE. Some analysts argue the "true" fair-value CAPE is now closer to 20–22 rather than the historical 16–17.

Interest rates change what a fair multiple looks like. This is the big one. When the risk-free rate on a 10-year Treasury bond is 5%, you need stocks to offer a competitive return — so you'd expect lower P/E ratios. When rates are near zero, stocks look more attractive by comparison, and higher multiples make some logical sense. The CAPE ratio, by itself, doesn't account for this. That's a meaningful gap. (There's a modified version called the CAPE yield spread that adjusts for this, but it's less widely quoted.)

It's a terrible short-term timing tool. Shiller himself has said this. A high CAPE can stay high — or get higher — for years before anything bad happens. Anyone who went to cash in 2013 because the CAPE looked elevated watched the market nearly triple before the 2020 COVID crash. Being right on valuation and wrong on timing is just being wrong.

The composition of the S&P 500 has changed. The index today is dominated by asset-light technology companies that earn high margins and require little physical capital. These businesses arguably deserve higher multiples than the industrial and manufacturing firms that dominated the index in the mid-20th century. Comparing today's CAPE to 1950's CAPE might be a bit like comparing mortgage rates to horse boarding fees. Directionally useful; not perfectly apples-to-apples.

None of these criticisms kill the CAPE ratio. They just mean you should treat it as one input among several rather than a smoking oracle.

What a High CAPE Actually Tells You About Future Returns

Here's where the CAPE ratio earns its keep. Over 10-to-20-year horizons, it's one of the better predictors of annualized returns the research has found. And the relationship is pretty intuitive: the more you overpay today, the less you get back tomorrow.

Research from Shiller's own dataset and replicated by others suggests that when CAPE is above 30, subsequent 10-year real returns for the S&P 500 have historically been low — sometimes in the low single digits annually, occasionally negative in real terms. When CAPE is below 10, subsequent 10-year real returns have historically been excellent — often double digits.

The catch? "10-year returns" is a long time to wait for a thesis to play out. And in the meantime you could be sitting in T-bills while the market gallops past you.

This is why CAPE matters more for retirement planning and long-term asset allocation than for deciding what to do with your brokerage account this Thursday.

How CAPE Connects to the Broader Market Picture

The CAPE ratio doesn't live in a vacuum. Markets are priced by investors who are simultaneously watching earnings growth, interest rates, geopolitical risk, and a hundred other signals. When you see big moves in assets that seem disconnected from fundamentals — gold spiking, bonds getting weird, individual mega-cap stocks swinging violently — that often reflects the same tension between elevated valuations and changing macro conditions.

Take earnings season for a large-cap tech company trading at a high multiple. When the market has priced in perfection, even genuinely strong numbers can disappoint — because "good" isn't good enough when you're paying a premium. That dynamic shows up clearly when you look at how investor reaction to big earnings beats can still send a stock lower. I wrote about exactly that kind of setup in Nvidia's Numbers Were Massive. Look Closer. — a case study in what "good but not perfect" looks like when expectations are sky-high.

On the rates side: when bond yields move sharply, the math on stock valuations changes in real time. Higher yields make future earnings worth less in today's dollars, which puts downward pressure on the multiples investors are willing to pay. That's a key reason geopolitical shocks that send oil prices higher and Treasury yields sliding can have complicated, sometimes counterintuitive effects on equity valuations. The piece on Oil, Bonds, and a Strait You Should Know by Name gets into that dynamic if you want to see it play out in a specific episode.

How to Actually Use This Number

A few practical frameworks that make more sense than "CAPE is high, sell everything":

Use it to calibrate expectations, not make trades. If CAPE is significantly above its historical average, lower your expected annualized return for the next decade. Don't abandon equities — just don't extrapolate recent returns into the future and plan your retirement around them.

Pair it with the 10-year Treasury yield. The "Fed Model" or CAPE yield spread subtracts the 10-year yield from the CAPE earnings yield (which is just 1/CAPE). If the spread is still favorable relative to history, stocks might not be as expensive as the CAPE alone suggests. If the spread has narrowed significantly — meaning bonds are competitive with stocks on a yield basis — that's when elevated CAPE gets more concerning. Policy decisions around Treasury debt and yields, like those tracked in stories such as Scott Bessent Just Blinked — and Gold Noticed, can shift this spread quickly.

Think about what you're buying specifically. An index-level CAPE tells you the average. Individual sectors and international markets have their own CAPE readings. Emerging markets and certain European indexes often trade at much lower CAPEs than the U.S. — whether that reflects genuine value or genuine risk is the work of actually researching those markets.

Don't let it paralyze you. A CAPE of 35 doesn't mean the market falls tomorrow. It might mean the next decade of returns is modest. If you're 30 years old and investing for retirement, "modest returns" for a decade followed by a mean-reversion cycle is still going to grow your money. Time is the great equalizer.

The Bottom Line on Valuation

Valuation matters — but it matters on the time horizon you're actually working with. The CAPE ratio is one of the smartest long-run valuation tools we have, and it has a real track record. But it's not a crystal ball, it's not a timing signal, and it wasn't designed to tell you whether to buy the dip this afternoon.

What it does tell you: when you're buying something everyone agrees is expensive, the implied return you're accepting is lower. That's not a disaster. It's just arithmetic. And arithmetic is better than vibes.

FAQ

What is a good CAPE ratio for the stock market?

There's no universally "good" CAPE number, but the long-run historical average for the U.S. market is roughly 16–17. Readings below that suggest the market is cheap relative to its own history; readings significantly above it suggest expensive. That said, some analysts argue the structural changes in the S&P 500's composition — particularly its shift toward high-margin technology companies — justify a higher fair-value baseline, maybe closer to 20–22. Treat the historical average as a reference point, not a redline.

Why does Robert Shiller use 10 years of earnings instead of one?

One year of earnings is too noisy. Corporate profits swing dramatically through economic cycles — collapsing in recessions and surging in booms — in ways that can make a terrific buying opportunity look expensive (when earnings have crashed) or a dangerous market look cheap (when earnings are temporarily elevated). By averaging a full decade of inflation-adjusted earnings, Shiller smooths out those distortions and gets a cleaner signal of the market's structural profitability. It's not that one year is useless; it's that ten years is more honest.

Has the CAPE ratio ever been wrong?

Plenty of times, depending on what you mean by "wrong." The CAPE stayed elevated throughout most of the 2010s bull market — anyone who used it as a sell signal in 2013 or 2014 missed enormous gains. It's also less reliable as an international comparison tool, since accounting conventions and market structures differ, making a "30 CAPE in the U.S." not directly comparable to a "30 CAPE in Japan." The ratio works best as a long-horizon return forecaster, not a short-term market call. Treat it as one piece of evidence, not a verdict.

Is the U.S. market always more expensive than international markets by CAPE?

Not always, but often in recent years, yes. The U.S. market has traded at a persistent CAPE premium to most developed and emerging market indexes. Part of that premium reflects the genuine quality difference — U.S. companies, especially large-cap tech, generate higher profit margins and return more capital to shareholders than many international peers. Part of it might be a true overvaluation. That gap is why some long-run asset allocators deliberately hold international equities as a valuation hedge: even if the U.S. continues to outperform operationally, a lower starting CAPE elsewhere can translate into better 10-year returns.

Can the CAPE ratio predict a market crash?

It can identify stretched valuations, but it can't tell you when a correction will happen or how large it will be. Every major U.S. market peak in modern history — 1929, 2000, 2007 — was preceded by an elevated CAPE. But an elevated CAPE didn't cause those crashes; it just meant the market was priced for perfection, leaving it more vulnerable when something went wrong. Think of CAPE like checking if a car is low on oil: it tells you there's added risk of a breakdown, but it doesn't tell you the breakdown is happening today or that it won't make it another 10,000 miles.