Simple vs. Compound Returns: Why Your Investment Statement Can Mislead You
September 18, 2026
Averaging a series of annual percentage returns (a simple/arithmetic average) overstates actual investment performance, because gains and losses don't offset symmetrically once you account for compounding. The metric that reflects what you actually earned is CAGR — compound annual growth rate.
Skip the math and get your answer instantly:
Open the Investment Calculator →The Classic Example
An investment gains 50% in year one, then loses 50% in year two. The simple average of +50% and −50% is 0% — suggesting you broke even. But $100 growing 50% becomes $150, and $150 losing 50% becomes $75. You actually lost 25% of your money, not 0%.
Why This Happens
A loss requires a larger subsequent gain to fully recover, because the loss shrinks the base you're gaining from. A 50% loss requires a 100% gain just to get back to even — not a 50% gain. Simple averaging treats percentage gains and losses as if they're symmetrical dollar amounts, which they aren't once compounding is involved.
CAGR: The Metric That Reflects Reality
Compound Annual Growth Rate (CAGR) = (Ending Value / Starting Value)^(1/years) − 1. For the example above, starting at $100 and ending at $75 over 2 years: CAGR = (75/100)^(1/2) − 1 ≈ −13.4% per year — a much more honest picture of the investment's actual annualized performance than a 0% simple average.
Frequently Asked Questions
Why is a 50% loss worse than a 50% gain is good?
Because percentage changes apply to a shrinking or growing base. A 50% loss cuts your balance in half; recovering that loss back to the original amount requires a 100% gain on the new, smaller balance — not another 50%.
What is CAGR?
Compound Annual Growth Rate — the single steady annual rate that would take your investment from its starting value to its ending value over the given number of years, accounting properly for compounding.
Should I trust an advertised 'average annual return'?
Check whether it's a simple (arithmetic) average or CAGR — a simple average of yearly returns tends to overstate real performance whenever returns are volatile, since it ignores the compounding effect of losses.
Does volatility always make simple averages misleading?
The more volatile the year-to-year returns, the bigger the gap between the simple average and the actual CAGR — a steady 7%-per-year investment has almost no gap, while a volatile investment swinging between large gains and losses can have a very large one.
How do I calculate CAGR myself?
CAGR = (Ending Value / Starting Value)^(1/number of years) − 1, expressed as a percentage.