Nominal vs real returns — and why it matters
A 10% return sounds great until you remember that 3% of it just kept pace with inflation. The nominal return is the headline number on your statement. The real return — nominal minus inflation — is the growth in purchasing power, and it is the only number that tells you whether you are actually getting richer.
For long-term plans, always model with real returns. If you assume 7% real and inflation comes in at 3%, your account statements will read about 10% — and your buying power will grow exactly as planned. If you assume 10% nominal without subtracting inflation, you will be quietly short by the time the plan matures.
Fees, taxes, and the drag you do not feel
A 1% expense ratio does not feel like much. Over a 30-year horizon, it can quietly evaporate 20–25% of your final balance — silently, every month, with no notification. The same is true of frequent trading taxes, advisor fees over 1%, and any product with hidden loads.
Before you enter an expected return, subtract everything that comes off the top: expense ratios, advisory fees, expected tax drag in taxable accounts. The number you put into the calculator should be the net return you actually keep.
CAGR vs average return — the math that exposes hype
If a fund returns +50% one year and −50% the next, its average return is 0%. Its CAGR is −13.4%. The CAGR is the honest one — it accounts for the fact that losses are mathematically harder to recover from than equivalent gains.
Whenever a marketing page advertises "average annual return," it is almost always the arithmetic mean, and almost always higher than the CAGR. Compute the CAGR yourself from the start and end values, and compare.
Common investment-return mistakes
- Using the recent decade's returns instead of long-run averages.
- Ignoring fees, taxes, and inflation when projecting "final value."
- Confusing average annual return (arithmetic) with CAGR (geometric).
- Modeling contributions you have not actually sustained in real life.
- Forgetting that the last year before withdrawal can wipe out a decade of gains — sequence-of-returns risk.