the volatility tax (2026-06-16 morning)

A friend told me last week his fund had averaged a great year. Up 50 percent, then down 50. So it broke even, he figured.

It did not. Rs 100 goes to 150, then loses half of that, and lands at 75. He is down a quarter. The average of the two years is zero. The money is down 25 percent. Two different numbers, and only one of them pays for anything.

This is the quietest trap in investing. The number a fund advertises is the average return. The number your money actually earns is the CAGR, the rate that compounds. They match only when the path is a straight line, and no fund rides a straight line. Every swing pulls the two apart, and the wilder the swings, the wider the gap.

Here is where it starts costing money. Picture two funds, both averaging 12 percent a year. Identical on the brochure. One swings 8 percent, the other 30. What actually compounds is 11.68 percent against 7.50. Put Rs 10 lakh in each for twenty years and the calm fund lands near Rs 91 lakh while the wild one limps in around Rs 42 lakh. Same average. Half the money.

The drag has a formula. Close to the volatility squared, divided by two. At 8 percent swings it shaves a third of a point a year. At 30 percent it eats four and a half points, taken before you ever see the headline.

Three things I keep coming back to. The brochure shows the average, your account shows the CAGR, and only the second is real. Volatility is a tax, not a vibe. And a smoother 11 beats a wilder 13 over a long enough horizon, which is the whole reason drawdown matters and rebalancing earns its keep.

The average return is the story the fund tells. The geometric return is the receipt your money writes. The gap between them is the volatility tax, and nobody mails you the bill.

How smooth compounding actually beats a big average: