Trading Is Hazardous to Your Wealth

This lesson is the thesis of this entire app, and it comes from a study of 66,465 real households, not a slogan. The people who traded the most made the least. Consistently.

Last verified 2026-07-16

The study, and what it actually compared

Barber and Odean obtained the trading records of 66,465 households at a large discount broker from 1991 to 1996 — real accounts, not survey answers about what people thought they'd earned.

They sorted households by turnover, meaning how much of the portfolio was traded per year, and compared returns across the groups. The most active fifth earned 11.4% annually while the market returned 17.9% over the same window.

Read those numbers carefully. The 17.9% is what that particular period delivered, not a general expectation for stocks, and the honest figure here is the roughly 6.5-point gap between the groups — that's the part attributable to activity rather than to the era.

Where the 6.5 points went

Three leaks, and only one of them appears on a statement. The bid-ask spread is paid on every round trip and is never itemised as a fee — you simply buy slightly above the midpoint and sell slightly below it.

Tax is the largest and most controllable. A position held under a year is taxed as ordinary income, up to 37%, instead of the 0/15/20% long-term rates. Selling at eleven months rather than thirteen can cost more than the trade was ever going to make.

The third leak is the one Barber and Odean singled out, and it's the one nobody budgets for: the stocks these investors sold tended to outperform the ones they bought. So the trades weren't merely expensive, they were pointed the wrong way — which is what turns overconfidence into a measurable cost rather than a personality trait.

The professionals don't clear this bar either

S&P's SPIVA scorecard tracks active funds against their benchmarks. In the Year-End 2024 edition, not one of the 22 US equity categories had a majority of active managers beat its benchmark over 15 years.

There's a real methodological objection worth carrying, because a lesson that only cites the convenient study is doing the thing this unit warns against. An Investment Adviser Association-backed critique argues SPIVA overstates the case by weighting all funds equally regardless of size and counting closed funds as automatic failures. Asset-weighted, the results look closer to a coin flip.

Take the critique seriously and the conclusion barely moves. 'Roughly a coin flip, before you pay the higher fee' is still not a reliable edge — and the people in question do this full time with research teams.