How to Spot a Bubble: Tulipmania to the S&P 500

Every generation of investors believes its bubble is the smart one. The Dutch in 1637 were not buying tulips because they were stupid - they were buying tulips because the price kept going up and everyone they knew was getting rich. The same was true of South Sea Company shares in 1720, dot-com stocks in 2000, US housing in 2007, and shitcoins in 2021. Learning how to spot a bubble before it pops is one of the more useful skills a long-term investor can develop, and the good news is that the playbook has barely changed in 400 years.

This article does three things. It walks through the six-stage pattern that economists have identified across every major mania since the 17th century. It tells you which books to read if you want the long version. And it gives an honest assessment of where the S&P 500 sits on that pattern in May 2026 - not a prediction, because anyone confidently predicting the top is selling something, but a framework you can use to make your own call.

Contents

• The Six-Stage Pattern Every Bubble Follows
• Minsky's Financial Instability Hypothesis
• What History Teaches: Tulips, the South Sea, and the Dot-Com Crash
• The Psychological Transition: Investing to Speculation
• The Books That Explain Speculation
• A Practical Bubble-Spotting Checklist
• The S&P 500 in 2026: Bubble or Just Expensive?
• What to Do If You Think You Are In One
• Frequently Asked Questions

The Six-Stage Pattern Every Bubble Follows

The economist Hyman Minsky developed a model of speculative manias that Charles Kindleberger later popularised in his classic Manias, Panics and Crashes. It has six stages, and once you have seen them you cannot un-see them.

1. Displacement. Something genuinely new arrives. The printing press, ocean trade routes, electricity, the railways, the internet, smartphones, blockchain, large language models. The new thing is not the bubble. The new thing is the spark.

2. Boom. Early adopters allocate capital, the new technology starts generating real economic activity, and prices rise. This stage can last years and is often justified by fundamentals. Owning Cisco in 1995 was an excellent decision. Owning Amazon in 1999 was also excellent. Most of the gains of any genuine boom are made here, by people who do not know they are early.

3. Euphoria. Prices start to rise faster than earnings. The narrative shifts from "this technology is useful" to "this asset only goes up." Cab drivers, hairdressers and family members start giving stock tips. New entrants flood in because they have watched their friends get rich and they do not want to be left behind. This is the stage Galbraith calls "the financial euphoria" - the moment collective psychology takes over from analysis.

4. Leverage and financial innovation. Money becomes easier to borrow against the asset. Margin debt rises. New products appear that let ordinary people get exposure they previously could not get: tulip futures in the 1630s, joint-stock companies in 1720, mortgage-backed securities in 2006, CFDs and crypto perpetuals today. Financial innovation always accompanies the late stages of a bubble. The innovation is usually a way of dressing up old-fashioned greed in a new legal wrapper.

5. Distress. Insiders start selling. The smartest money quietly steps back. The narrative cracks at the edges - a big firm posts unexpected losses, a fund gates redemptions, an analyst publishes a sell note and is mocked. Prices wobble. The official story is "healthy correction." The honest story is "the marginal buyer is gone."

6. Collapse and revulsion. Forced selling begins. Leverage works in reverse and amplifies the drop. The same crowd that piled in at stage three sells at stage six, often locking in catastrophic losses. The asset class is then shunned for a decade, which is usually when it becomes a sensible buy again.

If you can place an asset clearly in stages one or two, you are an investor. If you can only place it in stages three or four, you are speculating, whether you admit it or not. That is the framework. The rest of this article is detail.

Minsky's Financial Instability Hypothesis

The reason credit matters so much to the late stages of a bubble is captured in Hyman Minsky's financial instability hypothesis, which classifies borrowers into three categories that emerge in sequence during any long boom.

Stable economies are dominated by hedge finance. As a boom matures, more and more borrowers shift up the ladder. When the system reaches the point where a significant share of borrowing is Ponzi finance, the entire structure depends on prices continuing to rise. Any pause is enough to break it.

Minsky's central insight: stability itself breeds instability. The longer the good times run, the more participants assume the good times are permanent, and the more they take on the kind of debt that only works if the good times continue. The bust is built into the late stages of the boom by the very people most convinced there will not be one.

What History Teaches: Tulips, the South Sea, and the Dot-Com Crash

The specific asset changes. The human behaviour does not.

Tulipmania (1634-1637). Dutch tulip bulbs reached prices equivalent to the annual income of a skilled craftsman for a single rare bulb. The market was largely a futures market, settled with paper contracts in taverns - the leverage was structural even before the word existed. When prices broke in February 1637, contracts could not be enforced and an entire informal market evaporated in a week. Charles Mackay's Extraordinary Popular Delusions and the Madness of Crowds (1841) is the source most people quote, and modern historians have softened some of his more lurid claims, but the basic shape (displacement, boom, euphoria, leverage, collapse) is intact.

The South Sea Bubble (1720). The South Sea Company was granted a monopoly on trade with Spanish America. The actual trade barely existed - the asset was the story. Share prices rose roughly tenfold in a year, fuelled by parliament-sanctioned debt-for-equity swaps, easy credit, and a wave of copycat ventures known at the time as "bubble companies." One famously raised money for "an undertaking of great advantage, but nobody to know what it is." When confidence broke, the resulting bust ruined thousands, including, famously, Isaac Newton, who lost the equivalent of millions in today's money. Newton's verdict afterwards: "I can calculate the motions of the heavenly bodies, but not the madness of people." If the man who invented calculus could not spot the top, you probably cannot either.

The dot-com bubble (1995-2000). The internet was not a fake technology. It transformed the global economy and is the reason this article exists. The bubble was not in the technology - it was in the prices people paid for any company claiming to be part of it. The NASDAQ Composite roughly quintupled between 1995 and March 2000, then fell about 78% over the next two and a half years. Many of the era's superstar names (Pets.com, Webvan, eToys) never recovered. Many of the era's quieter names (Amazon, Microsoft) compounded into trillion-pound businesses. The lesson is not that technology bubbles are stupid. It is that paying any price for a story is stupid, regardless of whether the story is true.

Crypto (2020-2022). A textbook six-stage cycle compressed into 24 months: genuine technological displacement, real early gains, mass-market euphoria with celebrity endorsements, financial innovation in the form of leveraged perpetuals and DeFi yield, distress as Terra/Luna collapsed, then revulsion as FTX failed and Bitcoin fell ~75%. The pattern was identical to 1720. The only thing that had changed was the wrapper.

Every bubble had a real innovation underneath

One of the more uncomfortable lessons of bubble history is that almost every mania was built on top of a real technology or genuine economic change. The bubble was not in the idea. It was in the price.

This is why "but the technology is real" is a dangerous argument. The technology was real in 1999, and the NASDAQ still fell 78%. The technology was real in 1840, and the British railway boom still wiped out the savings of hundreds of thousands of middle-class investors. A real innovation is the necessary condition for a bubble, because without one the narrative cannot get going. It is not the sufficient condition for the price to be reasonable.

The Psychological Transition: Investing to Speculation

Underneath the six-stage Minsky model is a quieter psychological transition that the great bubble writers all describe. The shift is gradual and often invisible to the people going through it, which is precisely why it is dangerous.

This is the investing-to-speculation drift. Edward Chancellor traces it through four centuries of manias and the same words appear every time: "this is different," "the rules have changed," "the old guard does not understand."

John Kenneth Galbraith's contribution was to name the three engines that drive this drift:

1. Short financial memory. Most market participants have not personally experienced the previous crash. Roughly 25-30 years is the half-life of a hard-won market lesson. By the time a new generation reaches financial maturity, the people who lived through the last collapse are either retired or being dismissed as out of touch.
2. The belief that the situation is unique. "This time is different" is, in Galbraith's phrase, "the most expensive four words in finance." The certainty that a particular bubble is the smart one is itself one of the most reliable bubble markers.
3. Social contagion. Markets are not collections of independent decision-makers. They are collections of people who watch each other, who compare themselves to each other, and who feel acute pain at the sight of a neighbour getting rich while they sit on the sidelines. FOMO is not a modern phenomenon. It is the engine of every mania in recorded history.

The Books That Explain Speculation

If you want to internalise this pattern, four books cover most of what is worth knowing. They are also a pleasure to read.

Devil Take the Hindmost by Edward Chancellor. The definitive single-volume history of financial speculation in the English-speaking world. Walks you from the South Sea Bubble through the railway manias of the 1840s, the 1929 crash, Japanese real estate in the 1980s, and the early dot-com era. Long, but worth the time. The title comes from a stage-coach phrase used to describe what happens at the back of a speculative pile-on.

A Short History of Financial Euphoria by John Kenneth Galbraith. Eighty-seven pages, readable in an afternoon, and very nearly the perfect book on bubbles. Galbraith identifies the recurring features in plain English: the rediscovery of leverage as "innovation," the equation of money with intelligence, and the speed with which the lessons of the previous crisis are forgotten. If you only read one book on this list, read this one.

Manias, Panics and Crashes by Charles Kindleberger and Robert Aliber. The academic anchor for the Minsky six-stage model described above. More analytical than the others and less narratively driven, but the framework it builds is what every other writer on bubbles is borrowing from, knowingly or not.

Extraordinary Popular Delusions and the Madness of Crowds by Charles Mackay (1841). The Victorian classic that put tulipmania, the South Sea Bubble and the Mississippi Bubble into general circulation. Some of the historical detail does not survive modern scrutiny, but the underlying observation - that financial manias are episodes of collective psychology, not of individual error - is the foundation that every later book builds on.

A bonus mention: Reminiscences of a Stock Operator by Edwin Lefèvre, the fictionalised memoir of legendary speculator Jesse Livermore. Not strictly about bubbles, but the best inside-the-mind-of-a-speculator account ever written, and the man's eventual fate (bankrupt, suicide) is the lesson that even the people who get the timing right usually still lose in the end.

A Practical Bubble-Spotting Checklist

Synthesising Kindleberger, Minsky, Galbraith and Chancellor, the following eight questions are the practical test. The more you can honestly answer "yes," the further into late-stage bubble territory you are.

1. Is there a genuine displacement? A real new technology, market, policy or financial innovation underneath the story?
2. Are valuations disconnecting from underlying cash flows? Are P/E, price-to-sales or yield-based metrics being explained away rather than respected?
3. Is leverage rising rapidly? Margin debt, household equity allocation, novel borrowing structures, vendor financing?
4. Are retail participants flooding in? Cab drivers giving stock tips. Family WhatsApp groups debating tickers. Brokerage account openings at record levels.
5. Are the lowest-quality assets outperforming? Profitless companies, meme tickers, junk crypto - all rising faster than the blue chips.
6. Are sceptics being dismissed emotionally rather than analytically? "OK boomer," "you just don't get it," "you missed the boat" arguments replacing actual valuation debate.
7. Are people buying mainly because prices have risen? The justification for owning the asset is the price chart itself.
8. Has speculation become culturally mainstream? Daytime TV segments. Tabloid coverage. Celebrity endorsements. Stock tips at the school gate.

A few "yes" answers describe an enthusiastic bull market. Most "yes" answers describe late-stage mania. Almost all "yes" answers describe a market that is one shock away from a Minsky moment.

The S&P 500 in 2026: Bubble or Just Expensive?

This is the question every UK investor with a global tracker is quietly asking, because the S&P 500 is approximately 60-65% of a typical cap-weighted global index like VWRP or HSBC FTSE All-World. If the S&P pops, your "diversified global tracker" is going to feel a lot less diversified.

Run it against the six-stage model honestly.

Displacement: yes, and obviously. Large language models, applied AI, and the infrastructure build-out (chips, data centres, power) are a genuine technological displacement. Nvidia, Microsoft, Meta, Alphabet, Amazon and Tesla have made enormous real cash flows on the back of it. This is not Pets.com territory.

Boom: yes, and well underway. The "Magnificent Seven" trade has now run for the better part of three years. Returns have been concentrated. In several recent calendar years, a handful of mega-cap names contributed the majority of the index's gains. Concentration of leadership is a feature of late-cycle bull markets.

Euphoria: present but not extreme. Retail participation, options activity, and sentiment surveys all sit at elevated levels. Mainstream financial coverage routinely treats double-digit annual returns as the baseline expectation rather than a historical outlier. People in non-investing jobs have opinions about Nvidia's product roadmap. None of this is 1999. All of it is closer to 1999 than to 2009.

Leverage: mixed. US household equity allocations are at or near historic highs. Margin debt is elevated but not at the post-2021 extremes. Importantly, the household-balance-sheet leverage that drove the 2008 collapse is not really present here. This is one of the strongest arguments against the "imminent crash" narrative: a bubble that pops without leverage usually deflates rather than detonates.

Distress: not yet visible. Insiders have been selling for some time, which is normal in a long bull market. There has been no banking accident, no major hedge fund failure, no equivalent of the Bear Stearns moment.

Collapse: by definition not.

The honest reading: the valuation picture looks bubbly (the Shiller CAPE has spent the last two years near levels last seen in 1999 and 2021), the breadth picture looks bubbly (a handful of stocks dominating), but the leverage picture does not. That is not "no bubble." It is "if there is a bubble, it is the kind that disappoints rather than detonates" - more like Japan 1989 (a 30-year drag on returns) than 2008 (a 18-month collapse and recovery).

That distinction matters more than the headline answer. If you are 25, a Japan-style outcome is genuinely scary because it would compress your equity returns for most of your accumulation period. If you are 50 with a global portfolio, a Japan-style outcome is uncomfortable but survivable, because the rest of the world (which is currently cheap on most measures) would probably do the heavy lifting.

What to Do If You Think You Are In One

You do not need to call the top. The historical record is brutal on people who try.

Stop buying on margin. This is the single biggest piece of self-protection in bubble conditions. Margin works in both directions, and the moment forced selling kicks in, the leveraged investor goes from "down 30%" to "wiped out" in a week. If you do not have margin debt, leverage cannot end your portfolio. If you do, it can.

Rebalance, do not run. If your target allocation is 70% global equities and equities have run to 85% of your portfolio, sell the difference and put it into bonds or cash. This is the closest thing to "selling the top" that is actually achievable, because it does not require any prediction - it just enforces discipline you already wrote down.

Tilt at the edges, not in the centre. If you are worried about US concentration in a cap-weighted global index, the response is to route new contributions into a value-tilted or equal-weighted alternative rather than to liquidate your existing holdings. Selling the core triggers tax in a GIA, locks in opportunity cost if you are wrong, and forces a re-entry decision that almost nobody gets right. Routing new money is cheap, reversible, and asymmetric.

Build a cash buffer worth taking seriously. Twelve to twenty-four months of expenses in NS&I or a high-yield account is not a return-killer. It is the thing that lets you not sell at the bottom and avoid the psychology of market crashes that catches most retail investors. If a Japan-style scenario plays out, the cash is what gets you through. If nothing happens, you have given up 1-2% of return on a fraction of your assets to buy genuine sleep.

Do not predict. Plan for the case where you are wrong. The smartest investors in history have been wrong about market timing. Newton was wrong. Keynes was wrong. Buffett has been wrong. The point is not to be right. The point is to build a structure that survives being wrong - in either direction. A portfolio that compounds whether the bubble pops next week or in 2031 is worth more than a confidently-timed bet that is right once and wrong twice.

Frequently Asked Questions

What is the difference between a bubble and an expensive market?

A bubble has all six Minsky stages, including euphoria and leverage. An expensive market has elevated valuations relative to history but lacks the psychological and credit features. Markets can stay expensive for a long time without becoming bubbles. The S&P 500 has spent significant periods of the last decade at above-average valuations without collapsing. Use the six-stage checklist rather than a single price metric.

Is the Shiller CAPE ratio a reliable bubble indicator?

The Shiller CAPE (cyclically-adjusted price/earnings ratio) is a useful starting point but a notoriously poor short-term timing tool. It has been "elevated" for most of the last 25 years and has only twice (1999 and around 2021) reached levels widely accepted as bubble territory. Many investors who sold based on CAPE in 2015 are still waiting to be vindicated. Use it for long-horizon return expectations, not for selling decisions.

Can a global tracker protect me from a US bubble?

Partially. A cap-weighted global index like VWRP is currently around 60-65% US, so a US-led drawdown would hit it hard. Equal-weighted or value-tilted alternatives such as VHYL reduce US concentration meaningfully without abandoning global exposure. Holding some non-US-heavy exposure (developed Europe, emerging markets, UK income) is one way to soften the blow without trying to call the top.

Is crypto in a bubble right now?

Crypto has been through multiple complete six-stage cycles in 15 years and is plausibly mid-cycle in another one as of mid-2026. Unlike equities, most crypto has no underlying cash flows to anchor valuation, so the only honest valuation method is "what will the next buyer pay." That makes every crypto cycle structurally closer to tulipmania than to dot-com stocks. Treat any allocation as speculation, not investing, and size accordingly.

How long do bubbles usually last before they pop?

The euphoria stage typically runs 1-3 years before peaking. The South Sea Bubble peaked roughly 12 months into its mania phase. The dot-com peak came about three years after the NASDAQ acceleration began. The 2007 housing peak came about two to three years after the most aggressive subprime lending began. There is no fixed clock. The honest answer is that you can identify the stages but not the timing, which is exactly why a structural defence (rebalancing, no leverage, cash buffer) beats a predictive one.

Should I sell now and wait for a crash?

Almost certainly not. The historical record on people who go to cash anticipating a crash is bleak: most of them are right eventually but wrong for long enough that they underperform a simple buy-and-hold approach by a wide margin. The compromise that has the best evidence behind it is rebalancing back to your target allocation when equities run hot, holding a cash buffer worth taking seriously, and never using leverage. That gives you most of the protection without requiring you to be right about the top.

Further Reading:

Devil Take the Hindmost - Edward Chancellor - The definitive four-century history of financial speculation, from the South Sea Bubble to the dot-com era. The reference text for everything in this article. (Affiliate link - we may earn a small commission at no extra cost to you.)

A Short History of Financial Euphoria - John Kenneth Galbraith - Eighty-seven pages on why bubbles keep happening and why short financial memory is the most expensive cognitive bias in markets. Read it in an afternoon. (Affiliate link - we may earn a small commission at no extra cost to you.)

Read next:

• What Is Speculation?
• Surviving the 20% Drop: The Psychology of Market Crashes
• Adding a Value Tilt to Reduce US Tech Exposure

Capital at risk. The value of investments can fall as well as rise and past performance is not a guide to future returns. This article is general education and reflects the author's personal opinions; it is not personal financial advice. Tax rules can change and depend on your circumstances. If you are unsure what is right for you, speak to an FCA-authorised adviser.