Jeremy Siegel
Professor and author of Stocks for the Long Run
Born 1945
Compiled long-run historical return data for shares, bonds and cash, and argued equities have rewarded patient holders over long periods.
Biography
Jeremy Siegel, born in 1945, is an American economist and for many years a professor of finance at the Wharton School of the University of Pennsylvania. He studied at Columbia University and took a doctorate in economics at the Massachusetts Institute of Technology, where Paul Samuelson was among his teachers, before joining the University of Chicago and later Wharton.
His best known work is historical rather than theoretical. Stocks for the Long Run, first published in 1994 and revised several times since, assembles returns for American shares, bonds, bills and gold going back to the beginning of the nineteenth century and compares what each did to purchasing power over very long periods.
The conclusion that made the book influential is that the riskiness of shares depends heavily on how long you hold them. Over a single year equities are far more volatile than bonds; over holding periods measured in decades, the historical record he assembled showed them delivering more consistent real returns than bonds did, largely because inflation damages a fixed stream of interest payments more than it damages company earnings.
A later book, The Future for Investors, argued that the fastest growing companies and sectors have often been poor investments because their growth was already reflected in the price. Siegel has been a familiar commentator on markets and monetary policy for decades and has served as an adviser to an exchange-traded fund provider.
Career timeline
- 1945Born in Chicago.
- 1967Graduates from Columbia University.
- 1971Completes a doctorate in economics at the Massachusetts Institute of Technology.
- 1972Begins teaching at the University of Chicago.
- 1976Joins the Wharton School at the University of Pennsylvania.
- 1994Publishes Stocks for the Long Run, assembling two centuries of asset returns.
- 2005Publishes The Future for Investors, arguing that growth is often already priced in.
Investment philosophy
Siegel argues from data rather than from theory. His method is to gather the longest available record of what each asset class actually delivered, adjust it for inflation, and let the comparison make the case. That approach is why his conclusions are framed as historical observations rather than as predictions, and why the arguments against him are mostly arguments about the data.
The core observation is that risk is not a fixed property of an asset but a function of the holding period. A share is genuinely dangerous to someone who may need the money next year and behaves very differently for someone who will not touch it for thirty. Standard risk measures, which are calculated over short intervals, do not capture that difference at all.
The second strand is that inflation is the risk long-term savers actually face. A bond pays a fixed number of currency units, and inflation erodes what those units buy; a company can often raise its prices alongside costs. That is the mechanism behind his argument that equities have been the better long-horizon store of purchasing power, and it is a claim about mechanism rather than about market timing.
Key ideas
Tap any idea to expand a plain-English explanation, why it matters, and where to learn more.
The holding period changes the risk
The observation that shares look far riskier over one year than over thirty, because short-term volatility averages out over long periods while inflation does not.
It means risk cannot be assessed without knowing the time horizon, which changes what a sensible portfolio looks like for different savers.
A saver who will not touch the money for thirty years faces a very different question from one who needs it next spring, even holding identical assets.
Shares as an inflation hedge
The argument that company earnings have historically kept pace with inflation better than the fixed payments from bonds.
For a saver with decades ahead, losing purchasing power slowly is a larger threat than a temporary fall in price.
A bond paying a fixed coupon loses real value throughout an inflationary decade, while a company can often raise its prices alongside its costs.
The growth trap
The finding that the fastest growing companies and industries have often been disappointing investments because their growth was already in the price.
It separates a good business from a good investment, which are two different questions that beginners frequently merge.
Investors who bought the most exciting new industries of an era have frequently done worse than those who bought duller established ones.
Dividends compound quietly
The point that reinvested dividends account for a large share of the long-run real return from equities.
It shifts attention from price charts, which show only part of the return, to total return including income.
A price chart of an index over fifty years understates what a holder actually received, because it excludes every dividend paid along the way.
Judge asset classes on very long records
Comparing shares, bonds, bills and gold across two centuries rather than across the recent past.
Any short window is dominated by the conditions of that window. Long records show how each asset behaved across wars, inflations and depressions.
A comparison starting in 1980 tells you mostly about a long decline in interest rates, not about how bonds behave generally.
Major contributions
- Assembled and published one of the longest continuous records of American asset returns, covering shares, bonds, bills and gold.
- Made the case that equity risk depends on the holding period, which reframed how long-horizon savers are advised.
- Documented the growth trap, showing that fast-growing companies and sectors are often already priced for their growth.
- Brought total return, including reinvested dividends, into ordinary discussion of long-run performance.
- Wrote a book that has stayed in print through multiple revisions for three decades and is standard reading in finance courses.
Major successes
- Published Stocks for the Long Run in 1994, which became one of the most widely cited books on long-run asset returns.
- Taught finance at the Wharton School for decades and became one of its best known faculty members.
- Built the historical return series that later researchers have used, extended and argued with, which is its own kind of contribution.
- Wrote The Future for Investors in 2005, introducing the growth trap to a general readership.
Important books
- Stocks for the Long Run1994
His comparison of asset class returns across two centuries. Revised several times since first publication and still in print.
- The Future for Investors2005
On why the fastest growing companies and sectors have often made disappointing investments, and what that implies for how investors choose.
Influence on investors
Siegel supplied the historical evidence behind a great deal of modern retirement advice. The convention that a saver with decades ahead should hold mostly equities, and shift toward bonds as the horizon shortens, leans directly on the long-run return comparisons his book made accessible.
His work also popularised thinking in real terms. Presenting every asset class after inflation, rather than in nominal figures, is now standard practice in long-horizon analysis, and it makes the case for equities and against cash far more visible than nominal comparisons do.
Criticisms and debates
A balanced view includes the main criticisms and open debates, presented neutrally.
- Later research, notably by Edward McQuarrie, rebuilt the nineteenth-century record from primary sources and found early United States share returns lower and bond returns higher than the standard series showed.
- The evidence is drawn almost entirely from the United States, which was the most successful equity market of the period. Studies covering many countries find far less consistent results.
- Long-run averages hide the experience of individual investors, since somebody who begins at an unfortunate point can spend most of an investing lifetime behind.
- The argument that shares are safe over long horizons can encourage savers to take more equity risk than their actual circumstances, income stability or temperament support.
- His frequent public forecasts about market levels and interest rates are a different activity from the historical research, and they have been mixed in the way market forecasts generally are.
Lessons for investors
Plain-English takeaways. Context for learning, not advice to buy or sell anything.
- 1How risky an asset is depends on how long you intend to hold it.
- 2For a long-horizon saver, losing purchasing power slowly is the risk that does the most damage.
- 3A fast-growing company is not automatically a good investment, because the growth may already be in the price.
- 4A price chart understates what shareholders actually received, because it leaves out every dividend.
Notable quotes
“The longer the holding period, the better stocks look relative to bonds.”
“Stocks have historically been a better long-run hedge against inflation than bonds.”
Frequently asked questions
Who is Jeremy Siegel?
Jeremy Siegel is an American economist, born in 1945, and a longtime professor of finance at the Wharton School. He is best known for the book Stocks for the Long Run.
What is Stocks for the Long Run about?
It assembles returns for American shares, bonds, bills and gold going back to the early nineteenth century, adjusts them for inflation, and compares how each preserved and grew purchasing power over long periods.
What is the growth trap?
It is Siegel's finding that the fastest growing companies and industries have often been poor investments, because their expected growth was already reflected in the prices investors paid.
Does time really reduce the risk of shares?
His historical data shows real equity returns becoming more consistent over long holding periods, but this is a claim about the past and about the United States in particular, and it is disputed by researchers using other data.
Why are shares described as an inflation hedge?
Because companies can often raise prices as their costs rise, so earnings tend to move with inflation, whereas a bond pays a fixed sum whose purchasing power inflation steadily reduces.
What are the criticisms of his research?
The main ones are that the early data has been revised downward by later researchers, that the evidence is heavily United States focused, and that long-run averages can encourage more equity risk than an individual can actually bear.
What is the Siegel constant?
A name others gave to his finding that the long-run real return on US shares was strikingly stable across the nineteenth and twentieth centuries. Critics question how reliable the earliest data is, and a historical average is a description of the past rather than a rate anyone is owed.
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