How to Compare a Stock's Performance to Its Sector

Your stock closed the quarter up 12%. On its own chart that looks like a good three months, yet the chart can’t tell you whether the company did anything special or simply rode along with every other stock in its group, and that difference decides whether the rally says anything about the business. For that you need a benchmark and one subtraction.

Pick the benchmark

The usual benchmark is a sector ETF. Sector funds are broad, though: one technology fund can hold chipmakers, software firms and hardware makers. Those groups often split in the same quarter. An industry fund is narrower, closer to the company’s actual competitors, and usually the fairer comparison when one exists with enough assets and trading volume to be priced sensibly.

Start from what the company sells. A regional bank goes against a regional bank fund. A company that earns most of its revenue from one product line should be measured against a fund holding the other companies that sell that product, since those are the businesses facing the same customers and moving through the same cycle.

Then check how the fund is built before you trust it.

Chart both from the same start date

Most charting tools have a compare or overlay function. Add the ETF’s ticker. Switch the axis to percent change. Both lines now start at zero on the date you pick, and the gap between them at any later point on the chart is the difference in performance over that stretch, read straight off the axis.

The start date matters more than it looks. Begin the comparison the day after a sharp drop in your stock and it will look like a leader; begin it the day before and it will look like a laggard, even though the same prices sit on the chart in both cases. Pick a start that means something. The day you bought works. So does the last earnings report.

Do the subtraction

The quick version is one line of arithmetic.

Those 7 points belong to the company, at least as a first guess. The other 5% happened to the whole group. The argument for making this subtraction a habit is in subtract the sector’s move.

Draw a relative strength line

Divide the stock’s price by the benchmark’s price. Plot the result over time. Some charting tools build this relative strength line for you with a ratio function, usually entered as the two tickers with a slash between them, and if yours doesn’t, a spreadsheet with two columns of daily closing prices and a third column dividing one by the other does the same job.

The level of the line means nothing. Its direction is the whole point. Rising means the stock is outperforming and falling means it’s lagging. Flat means they move together.

The ratio divides the growth factors, 1.12 ÷ 1.05. Subtraction doesn’t. Over a quarter the gap is small. Over years, or with big moves, it widens enough to matter, so choose one method and keep using it every time you line up one period against another, or the figures you compare will be measuring slightly different things.

The line also shows timing. A stock that beat its sector by 7 points in a quarter could have done it steadily, or in one day on an earnings report while lagging on every other day. The line shows you which.

Check what the ETF holds

A benchmark is only as fair as its holdings. Open the fund’s holdings list. Look at the top ten names and their weights. Many sector funds weight by market value, so the largest companies can make up a big share of the fund, and if your stock is one of those top holdings you are partly comparing it with itself, which pulls the difference toward zero for reasons that say nothing about the business. Reading an ETF fact sheet shows where the weights and index method sit.

Where the fund is dominated by a handful of giants and your company is small, an equal-weight version of the same sector, if one exists, is often a closer match to how the typical stock in the group behaved.

What skews the comparison

Dividends are the first thing. A price chart ignores them. If the stock pays a large dividend and the ETF pays little, a price-only comparison understates the stock over long periods, so use total-return data where your tool offers it.

Risk is the second. A stock with a high beta tends to move further than the market in both directions, so beating the sector in a rising quarter may reflect that sensitivity more than anything the company did. Check the same comparison over a falling stretch before crediting the business.

Third, one period proves little. Run the comparison over two or three windows, a quarter, a year and the time since the last earnings report, and see whether the answer holds across them.