Position sizing: the quiet discipline

You can pick the right stock and still lose money. Buy too much of it and a routine drawdown shakes you out at the bottom; buy too little and being right barely registers. Position sizing — how much of anything to own — decides more outcomes than stock selection does, and it gets a fraction of the attention. Here is how this desk thinks about the discipline.

Conviction is not a licence

A high score on a pick is a statement about the evidence, not an instruction to concentrate. The most dangerous portfolio is a collection of best ideas held at sizes chosen by enthusiasm. Enthusiasm is at its maximum precisely when a thesis is freshest and least tested — which is exactly when size should be most restrained. Sizing rules exist to protect investors from their own certainty, ours included.

Survive first, compound second

The arithmetic of loss is brutally asymmetric: a position that halves must double just to get back to even. Deep drawdowns do not just cost money — they cost the capital and the composure needed for the next opportunity. This is why sensible frameworks cap single positions and, less obviously, cap clusters: five separate holdings that all depend on the same interest-rate outcome are closer to one large position wearing five tickers.

Size to the downside, not the dream

The common approach sizes positions by how much they could make. The disciplined approach sizes by what happens if the bear case wins: how much is lost if this thesis is simply wrong, and can the portfolio absorb that calmly? A position is correctly sized when the worst published scenario would be unwelcome but boring. If being wrong would be catastrophic, the position is too big — whatever the upside.

Add on evidence, not on price

Averaging into a falling position rewards the market's disagreement with more capital. A cleaner rule: add when the thesis strengthens — when the tripwires in the bear case keep failing to trigger — not merely when the price gets cheaper. Price is an opinion. Evidence is a reason.

Why we publish principles, not prescriptions

The right size for any position depends on circumstances only the investor knows — total wealth, liabilities, horizon, temperament. That is personal advice, and we do not give it. What we publish is the discipline itself, because the discipline is general even though the numbers never are.

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General information only — not personal financial advice. Research access is offered to wholesale investors under s708 of the Corporations Act.