Time is the secret ingredient of investing, a market veteran says. Over many decades, diversified stock index funds have produced extraordinary results.

Forget about the upheaval in the Middle East. Don’t dwell on Russia’s war with Ukraine, U.S. tariffs and the budget deficit — or just about anything else that has been dominating news coverage and threatening to undermine the markets.

These issues are critical right now, undeniably. But history suggests that they will be irrelevant in your investing life, if your horizon is long enough.

Instead, focus on just one thing: the remarkable record of compounded, reinvested stock returns over many decades. That’s the message of Charles D. Ellis, a pioneer of diversified index fund investing, who has distilled decades of experience and study into a deliberately simple new book, published in February by Wiley: “Rethinking Investing: A Very Short Guide to Very Long-Term Investing.”

“The secret to investing, in my view, is