THOSE WHO LIVE VERY long lives sometimes face an unfair irony: The accomplishments of even towering figures can lose their luster over time—not because they’re proven wrong, but because the ideas they developed become so widely accepted that we forget they were once innovations. The investment world lost one such towering figure last week: the economist Harry Markowitz, who was age 95.
Markowitz first came to prominence in the early 1950s, when his PhD thesis,

IN 2014, AN INVESTOR asked Charlie Munger—Warren Buffett’s second-in-command—why he wasn’t investing in Apple. Munger responded that, “No matter what their financial statements showed,” he’d never have a high degree of confidence in the company. “It’s just too hard.”
Buffett agreed. But things changed. Today, Buffett’s Berkshire Hathaway is Apple’s third-largest shareholder, with holdings valued at more than $150 billion.
What should we conclude from Buffett’s about-face? In recent weeks, I’ve referenced studies on market timing and trading.

MY PORTFOLIO HAS bounced back nicely from October 2022’s stock market low—and that’s a problem: I’ve learned over the decades that I’m not good at handling prosperity.
At issue is the question of when to rebalance my portfolio, in this case selling stocks and buying bonds to bring them back into line with my target percentages. Among experts, there’s no agreed-upon strategy, which is almost an invitation to bad behavior. We investors do better with hard-and-fast rules.

WHAT DO WALL STREET analysts, magazine editors, economists and academics have in common? They’ve all found it virtually impossible to make accurate market forecasts. That’s why Vanguard Group founder Jack Bogle gave this advice to investors: When markets go haywire, “Don’t do something. Just stand there.”
Warren Buffett has given the same advice. In 2008, here’s how he explained it: “In the 20th century, the United States endured two world wars and other traumatic and expensive military conflicts;

PEOPLE WHO INVEST in the stock market and people who bet on horses both hope to win. I expected the efficiency and behavioral finance factors that rule the stock market to have similar effects on horse betting. Instead, I found just the opposite.
The story begins 40 years ago. A few years after we were married, I suggested to my wife that we spend a day at the fabled Saratoga Race Course in Upstate New York and watch the thoroughbreds run.

A WHILE BACK, I WAS speaking with a mutual fund manager. In describing one of his fund’s stocks, he noted, “I owned it for a while, then I sold it, but then I bought it back.” It was a surprising comment since frequent trading is, in most cases, unproductive. Indeed, Warren Buffett has often said that his preferred holding period for an investment is “forever,” and many see that long-term mindset as crucial to his success.

THE DOUBLE-DIGIT recovery by the S&P 500-stock index this year has been driven almost entirely by seven mega-cap stocks: Apple, Google, Microsoft, Amazon, Meta, Tesla and Nvidia. In fact, these seven stocks now comprise more than 25% of the index.
Since our family is heavily invested in a mix of the S&P 500, U.S. technology and growth funds, plus some individual tech stocks, I began to worry about our portfolio’s investment concentration. I tallied our positions in these seven stocks across all our accounts.

NEW MORNINGSTAR research on bond funds echoes what the late Jack Bogle preached—and proved—for decades: Costs are the greatest predictor of fund performance, not stock or bond selection prowess. In investing, you get what you don’t pay for, said Bogle, Vanguard Group’s founder and creator of the first index mutual fund.

There’s a school of thought that claims it’s easier for active bond fund managers to beat their indexes than it is for their stock fund colleagues.

NASSIM NICHOLAS TALEB has written a trilogy on the topic of chance: Fooled by Randomness, The Black Swan and Antifragile. I didn’t find these three books to be easy reading, plus Taleb has strong opinions, which may turn off some readers. Still, there’s a host of investment lessons to be culled from his works.
Taleb argues that randomness plays a powerful role in financial markets and,

SERIES I SAVINGS bonds have garnered a lot of press over the past year. Thanks to higher inflation, these bonds have become a lot more attractive. Although savings bonds have historically been a go-to gift for birthdays, baptisms and bar mitzvahs, they’re more complicated than you might think. I bonds have a number of features that can confuse the average investor, me included.
Series I savings bonds, or I bonds, are designed to protect an investor from losing money to inflation.

LOOK AT THE STOCK market, and you’ll see that certain stocks often do better than others. Technology shares have been standout performers over the past 10 years, and health care stocks have done very well.
But research has also found that certain types of stocks have done better than others. Smaller-company stocks, for example, have outpaced those of larger firms. In the academic literature, characteristics like this, which are correlated with outperformance,

YOU’VE PROBABLY HAD the same experience I’ve had when shopping for clothes. Spring’s in the air—a great time to take advantage of the local clothing store’s annual winter clearance sale. You buy that Ralph Lauren cashmere sweater at 20% off and jaunt home basking in glory. But the next day, while out for a walk, you peek at the store’s window display and see the same sweater, but now marked down 30%. You return home bemoaning your impulsivity.

YOU’VE PROBABLY never heard of Carolyn Lynch. Shopping for groceries, she noticed a new display of panty hose packaged in colorful plastic eggs. She bought a pair, tried them on and loved them. She told her husband, Peter Lynch, the celebrated manager of Fidelity Magellan Fund and vocal advocate of “investing in what you know.” He promptly bought the stock. L’eggs became one of the most successful women’s consumer products of the 1970s.
I recently had my own L’eggs moment.

A FEW YEARS BACK, I related a story about the comedian Joan Rivers. Her daughter, Melissa, likes to joke that her mother was always very consistent. Wherever she was, she would always drive at 40 miles per hour, whether it was on the highway, in a school zone or in the driveway.
This is funny, but it also illustrates a key challenge for investors. On the one hand, it’s important to be consistent. But at the same time,

EMBARRASSED BY YOUR impulse to try the “sell in May and go away” gambit? Don’t be. You’re in good company. Selling stocks in the spring and returning in autumn was a favorite pastime of London financiers and bankers, who abandoned the steamy city for cooler vacation destinations. They resumed stock trading around St. Leger’s, the day of the last leg of English horse racing’s Triple Crown.
The tendency of global stock markets to rise less in the six months from May to October,