The past year for DexCom (NASDAQ:DXCM) investors has not been profitable

It's easy to match the overall market return by buying an index fund. Active investors aim to buy stocks that vastly outperform the market - but in the process, they risk under-performance. Unfortunately the DexCom, Inc. (NASDAQ:DXCM) share price slid 44% over twelve months. That's disappointing when you consider the market returned 11%. Longer term shareholders haven't suffered as badly, since the stock is down a comparatively less painful 25% in three years. Furthermore, it's down 18% in about a quarter. That's not much fun for holders. Of course, this share price action may well have been influenced by the 9.8% decline in the broader market, throughout the period.

So let's have a look and see if the longer term performance of the company has been in line with the underlying business' progress.

We've discovered 1 warning sign about DexCom. View them for free.

While the efficient markets hypothesis continues to be taught by some, it has been proven that markets are over-reactive dynamic systems, and investors are not always rational. By comparing earnings per share (EPS) and share price changes over time, we can get a feel for how investor attitudes to a company have morphed over time.

Even though the DexCom share price is down over the year, its EPS actually improved. It could be that the share price was previously over-hyped.

By glancing at these numbers, we'd posit that the the market had expectations of much higher growth, last year. But other metrics might shed some light on why the share price is down.

DexCom managed to grow revenue over the last year, which is usually a real positive. Since the fundamental metrics don't readily explain the share price drop, there might be an opportunity if the market has overreacted.

The image below shows how earnings and revenue have tracked over time (if you click on the image you can see greater detail).

DexCom is well known by investors, and plenty of clever analysts have tried to predict the future profit levels. Given we have quite a good number of analyst forecasts, it might be well worth checking out this free chart depicting consensus estimates.

A Different Perspective

While the broader market gained around 11% in the last year, DexCom shareholders lost 44%. Even the share prices of good stocks drop sometimes, but we want to see improvements in the fundamental metrics of a business, before getting too interested. Unfortunately, last year's performance may indicate unresolved challenges, given that it was worse than the annualised loss of 5% over the last half decade. We realise that Baron Rothschild has said investors should "buy when there is blood on the streets", but we caution that investors should first be sure they are buying a high quality business. I find it very interesting to look at share price over the long term as a proxy for business performance. But to truly gain insight, we need to consider other information, too. Consider for instance, the ever-present spectre of investment risk. We've identified 1 warning sign with DexCom , and understanding them should be part of your investment process.

Of course DexCom may not be the best stock to buy. So you may wish to see this free collection of growth stocks.

Please note, the market returns quoted in this article reflect the market weighted average returns of stocks that currently trade on American exchanges.

Have feedback on this article? Concerned about the content? Get in touch with us directly. Alternatively, email editorial-team (at) simplywallst.com.

This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.