The 25% rule of thumb
A 1% annual investment fee reduces a 30-year portfolio by approximately 25% versus the no-fee baseline. This is not 1% per year (30% total), but rather 25% of the final balance. The compounding math is unforgiving: each year the fee reduces both current returns and all future returns that would compound from that reduced base.
Over longer horizons the damage escalates. A 1% fee over 40 years costs roughly 30% of the terminal value. A 2% fee (common in some asset classes and advisors) costs roughly 50%. This explains why even 'small' fees can dwarf the value of active management or specialized strategies.
Fees in bull and bear markets
Fees hurt equally in both rising and falling markets. In a 20% down year, a 1% fee is still 1%, applied to a shrinking portfolio. Investors who pay for 'downside protection' from expensive active managers receive neither protection nor outperformance on average, yet still forfeit the full fee. Low-cost passive investing wins by default because it sidesteps the fee penalty while capturing full market exposure.