Which stocks drive your DEGIRO portfolio's return? Contribution per position

The return contribution of a position is not the same as its percentage return, but its weight in your portfolio multiplied by that return; in this article's worked example, a position that is 80% of the portfolio with a 5% return (4.0 percentage points) contributes more to the 7% total return than a position that is 20% with a 15% return (3.0 percentage points) — even though the latter looks like the stronger performer at first glance.

The trap: the highest return isn’t the biggest driver

Rank your positions by percentage return, and the outlier at +40% immediately stands out as the “top performer.” But if that position was only 2% of your portfolio, it barely moved the needle on your overall result — while a boring position returning 5% that made up 80% of your portfolio may have been the real engine behind your gains. We see this pattern come up again and again: investors celebrate the +40% outlier in their overview, while it only carries 2% of the portfolio’s weight and the boring 80% position did the real work. Percentage return and return contribution are two different questions.

What return contribution actually measures

Return contribution weighs a position’s return by its weight in your portfolio:

Contribution of a position = weight of the position × return of the position

Add up the contributions of all positions, and — for a portfolio unchanged over the period — you arrive at the total portfolio return, so you can see exactly which position caused which share of that total. In professional investing this is called “contribution to return” or performance attribution: the same principle fund managers use to explain which holding actually drove their return.

Buy or sell along the way, and this simple formula becomes an approximation — an exact contribution requires calculating with daily reweighted weights, which in practice is only manageable with automation. For the total return itself, including deposits along the way, see calculating your DEGIRO return.

Worked example

Your portfolio consists of two positions. Position A is 80% of your portfolio and returned 5%. Position B is 20% of your portfolio and returned 15%.

Contribution of position A: 80% × 5% = 4.0 percentage points

Contribution of position B: 20% × 15% = 3.0 percentage points

Total return: 4.0 + 3.0 = 7.0%

At first glance, position B (15% return) looks like the stronger performer than position A (5% return). But in reality, position A — purely because of its size — was the bigger driver behind your 7% total return. Size wins here. Not the fastest mover.

Why this tells you more than a ranking of returns

A ranking of percentage returns answers “which position did best,” but return contribution answers the question that actually matters for your overall wealth: “which position determined my result.” That distinction is exactly why heavy concentration in a single position — see also ETF overlap and concentration — can be both your biggest opportunity and your biggest risk: the same position that is now driving your gains is, in a downturn, just as much the engine behind your losses. The same, incidentally, goes for a position you’ve since sold — a closed position was, in hindsight, just as much a driver of your result. And to see how your weights looked at an earlier date, use portfolio time travel.

How ClearAnalyser calculates this for you

ClearAnalyser automatically calculates the exact return contribution of every position to your total portfolio return, so you don’t have to work out yourself which stocks or ETFs were actually the engine behind your gains — or your losses. How other tools handle this is shown in the DEGIRO portfolio tracker comparison.

Sources: CFA Institute literature on investment performance attribution.