With a price-to-earnings (or "P/E") ratio of 72.2x Cognex Corporation (NASDAQ:CGNX) may be sending very bearish signals at the moment, given that almost half of all companies in the United States have P/E ratios under 19x and even P/E's lower than 11x are not unusual. Nonetheless, we'd need to dig a little deeper to determine if there is a rational basis for the highly elevated P/E.

While the market has experienced earnings growth lately, Cognex's earnings have gone into reverse gear, which is not great. It might be that many expect the dour earnings performance to recover substantially, which has kept the P/E from collapsing. You'd really hope so, otherwise you're paying a pretty hefty price for no particular reason.

How Is Cognex's Growth Trending?

The only time you'd be truly comfortable seeing a P/E as steep as Cognex's is when the company's growth is on track to outshine the market decidedly.

Taking a look back first, the company's earnings per share growth last year wasn't something to get excited about as it posted a disappointing decline of 43%. This means it has also seen a slide in earnings over the longer-term as EPS is down 69% in total over the last three years. So unfortunately, we have to acknowledge that the company has not done a great job of growing earnings over that time.

Turning to the outlook, the next three years should generate growth of 47% each year as estimated by the analysts watching the company. Meanwhile, the rest of the market is forecast to only expand by 11% each year, which is noticeably less attractive.

In light of this, it's understandable that Cognex's P/E sits above the majority of other companies. It seems most investors are expecting this strong future growth and are willing to pay more for the stock.

The Bottom Line On Cognex's P/E

Typically, we'd caution against reading too much into price-to-earnings ratios when settling on investment decisions, though it can reveal plenty about what other market participants think about the company.

As we suspected, our examination of Cognex's analyst forecasts revealed that its superior earnings outlook is contributing to its high P/E. At this stage investors feel the potential for a deterioration in earnings isn't great enough to justify a lower P/E ratio. It's hard to see the share price falling strongly in the near future under these circumstances.

There are also other vital risk factors to consider before investing and we've discovered 1 warning sign for Cognex that you should be aware of.

You might be able to find a better investment than Cognex. If you want a selection of possible candidates, check out this free list of interesting companies that trade on a low P/E (but have proven they can grow earnings).

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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.