Concept
Cost Matters Hypothesis
The cost matters hypothesis is the simple arithmetic that investors as a group earn the market's return before costs, and therefore earn that return minus everything they pay after costs.
John Bogle, who founded Vanguard, built much of his case on this arithmetic rather than on a forecast. Every share in the market is owned by someone, so all investors together own the whole market. As a group, before costs, they earn the market's return. Once management fees, trading commissions, platform charges and taxes come out, the average investor has to trail the market. The economist William Sharpe reached the same conclusion by a different route in 1991. Bogle admitted the idea is closer to accounting than to theory. The key asymmetry is that returns are uncertain and fees are not. A fee is charged against your whole balance every year, not just against your gains. Compounding works for costs exactly as it works for returns, so a modest-looking 1% can take a large share of your final wealth over decades.
A real-life example
Maya invests $100,000 for 30 years and expects 7% a year. Her adviser's fund charges 1% in total annual costs. A broad index fund charges 0.05%. With no costs she would end near $761,000. The index fund leaves her about $751,000. The 1% fund leaves about $574,000. That one percentage point costs her roughly $177,000, which is close to a quarter of what the market actually delivered.
How to use it
- 1List the total yearly cost of every fund and account you hold: expense ratio, platform or custody fee, and trading commissions.
- 2Run that percentage over your real time horizon in a compound-interest calculator, then compare it with a low-cost index fund in the same asset class.
- 3Keep a pricier option only if you can name what the extra fee buys you that you could not get more cheaply. If you can't, plan the switch.