While not a mind-blowing move, it is good to see that the Align Technology, Inc. (NASDAQ:ALGN) share price has gained 20% in the last three months. But that cannot eclipse the less-than-impressive returns over the last three years. In fact, the share price is down 49% in the last three years, falling well short of the market return.

On a more encouraging note the company has added US$1.0b to its market cap in just the last 7 days, so let's see if we can determine what's driven the three-year loss for shareholders.

In his essay The Superinvestors of Graham-and-Doddsville Warren Buffett described how share prices do not always rationally reflect the value of a business. 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.

Align Technology saw its EPS decline at a compound rate of 36% per year, over the last three years. In comparison the 20% compound annual share price decline isn't as bad as the EPS drop-off. So the market may not be too worried about the EPS figure, at the moment -- or it may have previously priced some of the drop in. With a P/E ratio of 53.06, it's fair to say the market sees a brighter future for the business.

The company's earnings per share (over time) is depicted in the image below (click to see the exact numbers).

We like that insiders have been buying shares in the last twelve months. Having said that, most people consider earnings and revenue growth trends to be a more meaningful guide to the business. Dive deeper into the earnings by checking this interactive graph of Align Technology's earnings, revenue and cash flow.

A Different Perspective

Investors in Align Technology had a tough year, with a total loss of 11%, against a market gain of about 27%. However, keep in mind that even the best stocks will sometimes underperform the market over a twelve month period. Regrettably, last year's performance caps off a bad run, with the shareholders facing a total loss of 0.5% per year over five years. Generally speaking long term share price weakness can be a bad sign, though contrarian investors might want to research the stock in hope of a turnaround. 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. To that end, you should be aware of the 1 warning sign we've spotted with Align Technology .

Align Technology is not the only stock insiders are buying. So take a peek at this free list of growing companies with insider buying.

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

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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.