Most people judge diversification by counting. Four funds feels safer than one. Nine holdings feels safer than four. The instinct is reasonable and the arithmetic does not support it.
What actually matters is whether your holdings are exposed to different things. If everything you own rises and falls for the same underlying reason, then owning more of them spreads your money without spreading your risk.
That number is not a criticism of those funds. Each is cheap, well run, and does exactly what it says. It is a statement about what happens when you combine them: four fee schedules, four fund companies, and not quite two independent bets.
It is like packing four torches for a power cut and then discovering they all run off the same battery. You have four objects and one point of failure.
A factor genome is what you get when you stop describing a portfolio by its contents and start describing it by its exposures. Each holding is measured against a small set of well-studied return drivers, and the portfolio is the blend of those measurements.
- Market — how much you simply move with equities as a whole. Almost everything loads on this.
- Size — tilt toward smaller companies rather than larger ones.
- Value — tilt toward cheaper companies relative to their fundamentals.
- Profitability — tilt toward companies that earn more on what they own.
- Investment — tilt toward companies that expand their asset base cautiously.
- Momentum — tilt toward what has recently been going up.
Two more readings matter as much as the loadings themselves. Effective bets condenses the whole picture into one number: how many genuinely independent exposures you hold. And the unexplained share is the risk the factors cannot account for — specific to those particular holdings.
A high unexplained share is worth noticing rather than celebrating. It does not mean the portfolio is well diversified; it means the model cannot see what is driving it, which is a different and less comfortable situation.
Finisdom regresses each holding against Ken French’s published factor data — the Fama-French five factors plus momentum — and blends those fits, weighted, to position a portfolio. Blending needs no return history for the portfolio itself, so it works the moment you type your holdings in, but it assumes the holdings’ unexplained risks are unrelated. Treat the unexplained figure as a floor.
What are effective bets?
A count of how many genuinely independent risk exposures a portfolio carries, as opposed to how many positions it has. Four holdings that all load on the same factor score close to one, not four. It is the number that answers "how diversified am I really".
Is a low effective-bets number always bad?
No. Concentration is a fact about a portfolio, not a verdict on it — a deliberate single bet made with conviction is a legitimate choice. The problem is holding one bet while believing you hold six, because then the risk you are running is not the risk you think you signed up for.
Why do two funds with completely different holdings behave the same?
Because their factor exposures overlap even though their tickers do not. A large-cap growth fund and a technology fund may share almost no names while loading on the same combination of market and momentum, which is what actually drives their returns.