The Constellium SE (NYSE:CSTM) share price has fared very poorly over the last month, falling by a substantial 34%. Instead of being rewarded, shareholders who have already held through the last twelve months are now sitting on a 29% share price drop.

Since its price has dipped substantially, Constellium may be sending bullish signals at the moment with its price-to-earnings (or "P/E") ratio of 14.7x, since almost half of all companies in the United States have P/E ratios greater than 19x and even P/E's higher than 35x are not unusual. Nonetheless, we'd need to dig a little deeper to determine if there is a rational basis for the reduced P/E.

Constellium has been struggling lately as its earnings have declined faster than most other companies. It seems that many are expecting the dismal earnings performance to persist, which has repressed the P/E. If you still like the company, you'd want its earnings trajectory to turn around before making any decisions. If not, then existing shareholders will probably struggle to get excited about the future direction of the share price.

How Is Constellium's Growth Trending?

The only time you'd be truly comfortable seeing a P/E as low as Constellium's is when the company's growth is on track to lag the market.

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 31%. The last three years don't look nice either as the company has shrunk EPS by 65% in aggregate. Accordingly, shareholders would have felt downbeat about the medium-term rates of earnings growth.

Turning to the outlook, the next year should generate growth of 180% as estimated by the six analysts watching the company. That's shaping up to be materially higher than the 15% growth forecast for the broader market.

In light of this, it's peculiar that Constellium's P/E sits below the majority of other companies. Apparently some shareholders are doubtful of the forecasts and have been accepting significantly lower selling prices.

The Bottom Line On Constellium's P/E

The softening of Constellium's shares means its P/E is now sitting at a pretty low level. We'd say the price-to-earnings ratio's power isn't primarily as a valuation instrument but rather to gauge current investor sentiment and future expectations.

We've established that Constellium currently trades on a much lower than expected P/E since its forecast growth is higher than the wider market. There could be some major unobserved threats to earnings preventing the P/E ratio from matching the positive outlook. It appears many are indeed anticipating earnings instability, because these conditions should normally provide a boost to the share price.

Before you settle on your opinion, we've discovered 2 warning signs for Constellium (1 is a bit unpleasant!) that you should be aware of.

Of course, you might also be able to find a better stock than Constellium. So you may wish to see this free collection of other companies that have reasonable P/E ratios and have grown earnings strongly.

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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.