With a price-to-earnings (or "P/E") ratio of 7.7x Marathon Petroleum Corporation (NYSE:MPC) may be sending very bullish signals at the moment, given that almost half of all companies in the United States have P/E ratios greater than 19x and even P/E's higher than 34x are not unusual. Although, it's not wise to just take the P/E at face value as there may be an explanation why it's so limited.

With earnings that are retreating more than the market's of late, Marathon Petroleum has been very sluggish. 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.

What Are Growth Metrics Telling Us About The Low P/E?

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

If we review the last year of earnings, dishearteningly the company's profits fell to the tune of 40%. Unfortunately, that's brought it right back to where it started three years ago with EPS growth being virtually non-existent overall during that time. So it appears to us that the company has had a mixed result in terms of growing earnings over that time.

Shifting to the future, estimates from the analysts covering the company suggest earnings growth is heading into negative territory, declining 10% per year over the next three years. That's not great when the rest of the market is expected to grow by 10% per annum.

With this information, we are not surprised that Marathon Petroleum is trading at a P/E lower than the market. Nonetheless, there's no guarantee the P/E has reached a floor yet with earnings going in reverse. Even just maintaining these prices could be difficult to achieve as the weak outlook is weighing down the shares.

The Final Word

Using the price-to-earnings ratio alone to determine if you should sell your stock isn't sensible, however it can be a practical guide to the company's future prospects.

As we suspected, our examination of Marathon Petroleum's analyst forecasts revealed that its outlook for shrinking earnings is contributing to its low P/E. At this stage investors feel the potential for an improvement in earnings isn't great enough to justify a higher P/E ratio. Unless these conditions improve, they will continue to form a barrier for the share price around these levels.

Having said that, be aware Marathon Petroleum is showing 3 warning signs in our investment analysis, and 1 of those is potentially serious.

You might be able to find a better investment than Marathon Petroleum. 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.

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