Why does trading more often leave you with less?
Ask a room of drivers whether they are above-average and about eighty percent of hands go up. Investors are no different, and in markets the bill for that arithmetic arrives in cash.
Two flavours of overconfidence
Over-precision is the belief that your estimate is tighter than it is. Asked for a range you are "90% sure" contains the right answer, most people give a range that contains it barely half the time. In markets this becomes a price target quoted to two decimal places on a business whose next quarter is genuinely unknowable.
Illusion of control is the belief that effort translates into influence. More screens, more news, more monitoring — none of which moves the asset, all of which increases the urge to act, because action is what all that effort feels like it should produce.
Both converge on the same behaviour: trading more. And trading, unlike research, has a price list.
The bill, in numbers
Suppose each round trip — buy and later sell — costs about 0.5% all in: spread, commission, slippage, and any transaction tax. That is a deliberately modest figure for a retail-sized order.
An investor who turns over the whole portfolio twice a year pays roughly 1% a year in pure friction, before a single decision is judged right or wrong.
On €100,000 over 20 years:
- At 7% gross: about €387,000.
- At 6% — the same gross return, minus the 1% of friction: about €321,000.
About €66,000, roughly a sixth of the patient outcome, paid for activity that felt like diligence. And that is only the visible cost; studies of retail brokerage records have repeatedly found that the most active accounts also make worse timing decisions than the least active ones, so friction is the floor of the damage, not the whole of it.
The tell
Overtrading rarely announces itself as "I am overconfident." It announces itself as a sequence of individually reasonable decisions: trimming here, adding there, "rotating," "managing risk." Each one is defensible in isolation. The cost only becomes visible when you count them.
There is a diagnostic that cuts through the rationalisation: for each trade, ask what genuinely new information arrived between the last decision and this one? If the honest answer is "the price moved" or "I felt uneasy," that is not information — it is discomfort wearing information's clothes.
What actually helps
Not willpower. Friction, deliberately added: a written rule that positions are reviewed on a schedule rather than continuously; a cooling-off period between having an idea and executing it; a required written sentence stating the new fact that justifies the trade. Each of these converts an impulse into a decision — which is the only conversion that matters.
Try it now
- Count your trades over the last twelve months, multiply by your average position size, and multiply by 0.5%. That number is your annual friction bill. Express it as a percentage of your portfolio.
- For each of your last five trades, write the one sentence of new information that triggered it. Count how many sentences are actually about the asset rather than about the price or your mood.
- Below is one year of a widely held fund. Trace your own in-and-out pattern onto it — the points where you would have sold and bought back — then ask what one decision at the start of that year would have produced instead, and subtract the friction bill from step 1.