IT MIGHT SEEM LIKE an obscure academic question: Do stocks truly follow a random walk or can we count on them reverting to the mean? Depending on which side we favor in this debate, it can make a huge difference to how we invest—and to our confidence as investors.
Like me, many HumbleDollar readers have most or all their investment dollars in index funds. A key reason we invest this way: It’s impossible to predict which stocks will shine because they follow a random walk.

IMAGINE A MARKET genie offered you the choice between knowing the stock market’s return next year or the stock market’s average return over the next 10 to 15 years. Which would you choose?
I’m guessing that most people would prefer to know how the stock market will do next year. After all, that seems like more actionable information, plus who has the patience to wait a decade or longer? But for those with an investing time horizon of more than 10 years—the vast majority of us—knowing the stock market’s return over the next decade or longer is far more valuable information.

AN MIT PROFESSOR named Edward Lorenz published a paper in 1972 titled Predictability: Does the Flap of a Butterfly’s Wings in Brazil Set off a Tornado in Texas?

It was a catchy title. Though Lorenz didn’t mean it literally, the basic idea was that events in the physical world are highly interconnected—more so than they might appear.

The world of investments is similarly interconnected in ways that aren’t always visible. Just like the weather,

THE ECONOMY IS recovering and the stock market has recovered. The pandemic isn’t over, but it seems we’re past the worst, at least in the U.S. Feeling better? Take a deep breath, take a step back—and think about the past two decades.
Since early 2000, we’ve had three major stock market declines, or roughly one every decade:

In 2000-02, the S&P 500 tumbled 49%, excluding dividends. The first leg down was triggered by the bursting of the dot-com bubble.

IN RECENT MONTHS, there’s been a lot of handwringing about the stock market. Thankfully, we seem to be on the back end of the pandemic, but things remain far from perfect in the economy. Millions are still unemployed. And the government has had to spend trillions to get us through, adding to a federal debt that was already enormous.

Today, the economy is far more fragile than it was pre-COVID. And yet the stock market just keeps cruising to new all-time highs.

IS THIS A TIME TO be fearful? In Berkshire Hathaway’s 1986 annual report, Warren Buffett wrote, “We simply attempt to be fearful when others are greedy and to be greedy only when others are fearful.”
Make no mistake: There’s plenty of greed on display right now, whether it’s bitcoin, nonfungible tokens, Robinhood traders, GameStop or special purpose acquisition companies. All of this has some observers talking of a market bubble. Indeed, I suspect much of this nonsense “will end in tears,” a phrase my mother often used when trying to control her four rambunctious children.

IN THE ONGOING battle between those who believe that the stock market is in a bubble and those who don’t, you may have heard mention of something called CAPE, short for cyclically adjusted price-earnings ratio. Among market indicators, it has the strongest track record in predicting future market returns.
What does the CAPE ratio say about today’s market? It’s flashing red. According to CAPE, the U.S. stock market is more overpriced today than it has been at any time since the 2000 market peak.

ARE FINANCIAL MARKETS in a bubble? It’s a question I’ve never liked. I believe stocks and bonds are fairly valued most of the time, which means it’s extraordinarily difficult to beat the market averages and our best bet is to buy index funds.
But at the same time, during my adult life, there have been three key occasions when markets lost touch with reality: Japanese stocks and real estate in the late 1980s, technology stocks in the late 1990s and housing in the mid-2000s.

FOR MORE THAN a year, veteran investment manager Jeremy Grantham has been arguing that the U.S. stock market is in a bubble. And not just an ordinary bubble, but “an epic bubble… one of the great bubbles of financial history, right along with the South Sea bubble, 1929, and 2000.”
And yet, despite Grantham’s concerns, the market has only continued to march higher. In a recent interview, Grantham reiterated his concerns in even stronger terms.

ECONOMIST JOHN Maynard Keynes once observed that, “It is better for reputation to fail conventionally than to succeed unconventionally.” This is probably true in many realms. It’s certainly true in the investment world.
As the last 12 months have demonstrated, extreme and unexpected events can and do happen. But analysts whose job it is to make economic forecasts rarely go too far out on a limb. Sure, there are some forecasters who will take a chance with a view that’s far outside the consensus.

LAST YEAR WAS MY first bear market. I’ve been thinking a lot about it and about the astonishing stock market recovery that followed, so I’m better prepared for next time around. Here are three lessons I learned in 2020:
Lesson No. 1: Buy aggressively when markets fall. When the market crashed last February and March, I invested more in stocks. But I regret not having invested a lot more, despite having cash available.

THE CAPITOL WAS invaded by an angry mob 11 days ago. A week later, the House of Representatives voted to impeach the president. But if you’d been looking only at the stock market, you would have no idea.
Not only is the market higher today than it was the day before this all started, but also the VIX—the market’s “fear gauge”—is lower. From the perspective of the stock market, it’s been an ordinary few weeks.

I’VE LONG BEEN flummoxed by the difficulty people have managing money. It all seems so intuitive: Save, invest, repeat. Buy more when the market falls and a lot more when it crashes. Rebalance by adding more to losing asset classes—which today means buying value and international stocks.
Now, don’t get me wrong: I’m no financial genius. I’ve made my share of blunders. But I also know that being a do-it-yourself investor has saved me boatloads of money.

WHEN I THINK BACK on 2020—and I know we aren’t quite done with it yet—I’m reminded of the movie Alexander and the Terrible, Horrible, No Good, Very Bad Day. But to paraphrase Nietzsche, chaos isn’t all bad—if something positive ultimately emerges from it.
Below are five financial lessons that, in my mind, are worth carrying beyond this year:
1. Stock prices respond to news—but never in a predictable way. Leading up to the election,

YOU’RE DRIVING DOWN the highway when, all of a sudden, a maniac goes speeding by, weaving in and out of lanes. Most of us have experienced this—and most of us have the same reaction. “That guy is crazy,” we think to ourselves. “If he doesn’t slow down, someone’s going to get hurt.”
But suppose that an observer instead responded, “That fellow’s speed is perfectly appropriate. Nothing at all wrong with it.” Now, you might think it’s the observer who’s the crazy one.