A 50% rise followed by a 50% fall does not restore the starting value
A value of 100 rises 50% to 150 in the first year, then falls 50% to 75 in the second. The arithmetic average of the two annual returns is 0%, yet value has fallen 25%. CAGR measures compound growth from 100 to 75 over two years, about −13.40%.
| Measure | Flat path | Rise then fall |
|---|---|---|
| Value path | 100 → 100 → 100 | 100 → 150 → 75 |
| Arithmetic annual average | 0.00% | 0.00% |
| Total change | 0.00% | −25.00% |
| CAGR | 0.00% | −13.40% |
The arithmetic average adds each annual return and divides by the number of years. CAGR is the constant annual compound rate that reaches the same ending value. This table is arithmetic rather than product performance and excludes taxes, costs and currency changes.