Performance attribution

Why did this fund beat its benchmark?

When a fund does better than its index, the extra return came from one of two decisions: which sectors the manager put money into, or which stocks they picked inside those sectors. This page splits the difference between the two, and shows the working.

Method
Brinson-Fachler
Splits return into
Sector bets, stock picks
Sectors
5
Unexplained
Nothing
01 How it works

A manager makes two kinds of decisions.

Attribution grades each one separately. That matters, because a manager can be bad at the first and good at the second.

Decision one: which sectors

How much money goes into technology, into energy, into healthcare. If the fund holds more technology than its index does, that is a bet. The model scores the bet by asking whether technology beat the market as a whole — not just whether it made money.

Decision two: which stocks

Inside technology, which companies the fund actually holds. This is measured against the technology index itself, so the manager gets no credit for a sector that went up without their help.

Why the market average matters

An older version of this model gave a manager a positive score for overweighting any sector that made a profit. Brinson-Fachler fixed that. Putting extra money into a sector that returned 2% while the market returned 10% was a bad call, and it now scores as one.

02 One fund

Break down a single fund.

Pick a fund. The benchmark is filled in for you, and everything below updates.

Sector by sector

Every number is in percentage points of the fund's return

Sector bets next to stock picks

Which of the two did more work, in each sector

The same numbers, stacked

How much each sector added to the total

03 Two funds

Compare two funds.

Two funds can end up with the same return and have got there in completely different ways. This is where that shows up.

against

Who bet on what

Return from sector choices, in each sector

What each fund's return is made of

Sector bets and stock picks, stacked

04 Try it yourself

Change the weights.

Move a slider to hold more or less of a sector than the manager did. Everything below recalculates as you drag.

How much of each sector to hold

Weights add up to 100%

What if a sector crashes or rallies

These move a whole sector up or down. The fund and its index move together, so the manager's stock picking is unaffected — only the market underneath them changes.

Your sector bets against the manager's

Return from sector choices, in each sector

What it does to the total

The manager's portfolio next to yours

05 The maths

Three lines of algebra.

Written out for one sector at a time. Add them up across every sector and you get the fund's extra return exactly, with nothing left over.

Sector bets AEi = (wiWi) × (Rb,iRB)
Stock picks SEi = Wi × (Rf,iRb,i)
Both at once IEi = (wiWi) × (Rf,iRb,i)
They add up Σ (AE + SE + IE) = RPRB

What the letters mean

w — how much of a sector the fund holds
W — how much of it the index holds
Rf — what the fund made in that sector
Rb — what the index made in that sector
RB — what the whole index made

Two terms or three

The third term covers the overlap: holding extra of a sector and picking well inside it. Some people prefer to report two numbers instead of three, which you can do by folding that overlap into stock picks. Both versions still add up to the same total. A version that drops the third term without folding it in does not, and that is a common mistake.

Where the data comes from

The three funds here are made up, for teaching. The index names are real, but the holdings and returns are invented to show managers with different styles. Do not quote these numbers as anyone's actual performance.