Adam Smith Blog

Lessons from history in how to spot a bubble

Undercover Economist

Here are three noteworthy pronouncements about bubbles.

“Prices have reached what looks like a permanently high plateau.” That was Professor Irving Fisher in 1929, prominently reported barely a week before the most brutal stock market crash of the 20th century. He was a rich man, and the greatest economist of the age. The great crash destroyed both his finances and his reputation.

“Those who sound the alarm of an approaching?.?.?.?crisis have somewhat exaggerated the danger.” That was a renowned commentator who shall remain nameless for now.

“We are currently showing signs of entering the blow-off or melt-up phase of this very long bull market.” That was investor Jeremy Grantham on January 3 this year. The normally bearish Mr Grantham mused that while shares seem expensive, historical precedents make it plausible that the S&P 500 will soar from present levels of around 2,700 to more than 3,500 before the crash occurs.

Mr Grantham’s speculation is striking because he has tended to be a savvy bubble watcher in the past. But as any toddler can attest, it is not an easy thing to catch one before it bursts.

There are two obvious ways to diagnose a bubble. One is to look at the fundamentals: if the price of an asset is unmoored from the cash flow it is likely to generate, that is a warning sign. (It is anyone’s guess what this implies for bitcoin, an asset that has no cash flow at all.)

The other approach is to look around: are people giddy with excitement? Can the media talk of little else? Are taxi drivers offering stock tips?

At the moment, however, these two approaches tell a different story about US stocks. They are expensive by most reasonable measures. But there are few other signs of speculative mania. The price rise has been steady, broad-based and was hardly the leading news of 2017. Given how expensive bonds are, it is hardly a surprise that stocks also seem pricey. No wonder investors and commentators are unsure what to say or do.

It seems all so much easier with hindsight: looking back, we can all enjoy a laugh at the Extraordinary Popular Delusions and the Madness of Crowds, to borrow the title of Charles Mackay’s famous 1841 book, which chuckles at the South Sea bubble and tulip mania. Yet even with hindsight things are not always clear. For example, I first became aware of the incipient dotcom bubble in the late 1990s, when a senior colleague told me that the upstart online bookseller Amazon.com was valued at more than every bookseller on the planet. A clearer instance of mania could scarcely be imagined.

But Amazon is worth much more today than at the height of the bubble, and comparing it with any number of booksellers now seems quaint. The dotcom bubble was mad and my colleague correctly diagnosed the lunacy, but he should still have bought and held Amazon stock.

Tales of the great tulip mania in 17th-century Holland seem clearer — most notoriously, the Semper Augustus bulb that sold for the price of an Amsterdam mansion. “The population, even to its lowest dregs, embarked in the tulip trade,” sneered Mackay more than 200 years later.

But the tale grows murkier still. The economist Peter Garber, author of Famous First Bubbles, points out that a rare tulip bulb could serve as the breeding stock for generations of valuable flowers; as its descendants became numerous, one would expect the price of individual bulbs to fall.

Some of the most spectacular prices seem to have been empty tavern wagers by almost-penniless braggarts, ignored by serious traders but much noticed by moralists. The idea that Holland was economically convulsed is hard to support: the historian Anne Goldgar, author of Tulipmania (US) (UK), has been unable to find anyone who actually went bankrupt as a result.

It is easy to laugh at the follies of the past, especially if they have been exaggerated for the purposes of sermonising or for comic effect. Charles Mackay copied and exaggerated the juiciest reports he could find in order to get his point across.

Then there is the matter of his own record as a financial guru. That comment, this time in full, “those who sound the alarm of an approaching railway crisis have somewhat exaggerated the danger”, was Mackay himself, writing in the Glasgow Argus in 1845, in full-throated support of the idea that the railway investment boom of the time would return a healthy profit to investors. It was, instead, a financial disaster. In the words of mathematician and bubble scholar Andrew Odlyzko, it was “by many measures the greatest technology mania in history, and its collapse was one of the greatest financial crashes”.

Oddly, Mackay barely mentions the railway mania in subsequent editions of his book — nor his own role as cheerleader. This is a lesson to us all. It’s very easy to scoff at past bubbles; it is not so easy to know how to react when one may — or may not — be surrounded by one.

Written for and first published in the Financial Times on 12 January 2018.

My recent book is “Fifty Inventions That Shaped The Modern Economy”. Grab yourself a copy in the US or in the UK (slightly different title) or through your local bookshop.

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