What is CAGR, and why I look at it so much

CAGR stands for compound annual growth rate, and it answers a simple question: if your investment had grown at one steady rate every year, what rate would have taken it from where it started to where it ended? It's the honest per-year return, because it bakes in compounding — the fact that each year builds on the last — rather than treating the years as independent. I lean on it heavily, because it strips out the two things that most flatter a track record: a lucky single year, and the illusion created by simple averages. Once you see how averages mislead, CAGR is hard to give up.

What is CAGR, exactly?

It's the constant annual rate that connects your beginning and ending value over a number of years. If a sum grows to 1.6 times its start over five years, its CAGR is whatever yearly rate, compounded five times, equals 1.6 — about 9.9%. The formula is the ending value divided by the starting value, raised to one-over-the-years, minus one; the intuition is that it smooths a bumpy journey into the single steady rate that would have produced the same finish. That makes very different-looking histories directly comparable.

Why CAGR beats the average return

Because the simple average ignores compounding, and compounding is unforgiving of volatility. Take a stark case: up 50% one year, down 50% the next. The average return is zero — but you're left with 75 cents on the dollar, a CAGR of about −13.4% a year. A gentler example makes the everyday version clear: a +30% year followed by a −14% year averages 8%, yet compounds at only 5.7%. The bumpier the path, the wider the gap, and the average is always the more flattering of the two.

Why consistency is the whole game

Because compounding only stacks up if the base keeps growing, and big swings keep knocking it back down. Two strategies can post the same 8% average, but the steady one compounds at 8% while the volatile one compounds at 5.7% — and over decades that difference is enormous. This is why I care less about a spectacular year than about a rate that repeats: the snowball needs a hill it can roll down without hitting rocks. Steady and repeatable beats brilliant and erratic, almost every time.

How I use it

I judge strategies and indices by their CAGR, not by their best year or their advertised average. My portfolio's live CAGR sits at the top of the performance page, plotted against the S&P 500 over six years, and the compound-interest calculator shows what that per-year rate — sustained, not spiked — actually compounds into over decades. It also keeps expectations honest: a believable CAGR tells you what's realistic to plan around. And it points straight at the next idea — that protecting the rate from big losses matters more than chasing extra points, which is its own subject.