Fifty years. That is how long index funds have been around, and Bob Pisani sat down with Squawk on the Street, in a segment published August 31, to talk about it. Pisani spent decades as a CNBC markets correspondent on the floor of the New York Stock Exchange, explaining markets to ordinary people without ever making you feel dumb. That is a rarer skill than it sounds.

Now, whose memories are these? Some of them are mine, and I'll fold a few in alongside his. I opened my first brokerage account at twenty-three with $200 and a library book about index funds, and even then indexing was considered slightly odd. Actively managed funds were the default, and the idea that you could just buy the whole market and beat most professionals doing it was treated as something close to heresy. The heretics turned out to be right.

The math was always simple. Most actively managed funds, over long stretches, fail to beat their benchmark after fees. Jack Bogle launched the first index mutual fund for retail investors in 1976, and it got mocked as Bogle's Folly. That folly now sits at the center of trillions of dollars in retirement savings. I won't quote you a precise what-if number here, because fifty years of compounding at near-zero cost produces figures so large they sound fictional anyway, and I would rather you doubt me than doubt the arithmetic. Run it yourself with any long-term S&P 500 return series. The answer will make you sit down.

What I want younger investors to sit with is this, and this is me talking, not Pisani. The boring strategy won. It did not win every year, and it did not feel good during 1987, or 2000, or 2008, or 2020. I have lived through every one of those drawdowns with money on the line. The floor drops out and every instinct screams at you to do something, anything, sell, hide, wait for calmer days. The investors who ended up wealthy were mostly the ones who did nothing, or better yet, kept buying while everything was on sale.

Pisani watched the same story unfold from his perch on the exchange floor. What makes his perspective worth your time is that he saw the culture change, not just the numbers. Indexing went from a punchline to a punching bag to, now, the default advice most sensible people give their kids. Even Warren Buffett, a man who made his fortune picking stocks, wrote in his 2015 letter to shareholders, the one marking his 50th year running Berkshire Hathaway, that the trust set up for his wife should simply hold an S&P 500 index fund. When the best stock picker of his generation puts that in writing, the rest of us should listen.

But there is a wrinkle worth mentioning. When a majority of money flows through index funds, the market behaves a little differently than it did when stock pickers set prices. I wrote earlier this month about how stretched the S&P 500's valuation has become, and passive flows are part of why momentum can run longer than it used to. That does not make indexing a bad idea. It just means the discipline of rebalancing matters more now, not less.

Fifty years from now, I will not be here to check, but I suspect the advice will sound the same. Buy the whole market. Keep costs near zero. Add money on a schedule whether the headlines are cheerful or miserable. Rebalance once a year and get on with your life.

Congratulations to Pisani on the milestone coverage, and to everyone who ignored the mockery in 1976 and just kept buying. The joke, it turns out, was on everybody else.

As always, this is my perspective and not professional financial advice. Talk to a qualified advisor before making decisions with your own money.