The Nanjing Port Co., Ltd. (SZSE:002040) share price has fared very poorly over the last month, falling by a substantial 27%. The drop over the last 30 days has capped off a tough year for shareholders, with the share price down 28% in that time.

In spite of the heavy fall in price, Nanjing Port may still be sending bullish signals at the moment with its price-to-earnings (or "P/E") ratio of 20.9x, since almost half of all companies in China have P/E ratios greater than 27x and even P/E's higher than 48x are not unusual. However, the P/E might be low for a reason and it requires further investigation to determine if it's justified.

For instance, Nanjing Port's receding earnings in recent times would have to be some food for thought. One possibility is that the P/E is low because investors think the company won't do enough to avoid underperforming the broader market in the near future. However, if this doesn't eventuate then existing shareholders may be feeling optimistic about the future direction of the share price.

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

There's an inherent assumption that a company should underperform the market for P/E ratios like Nanjing Port's to be considered reasonable.

Retrospectively, the last year delivered a frustrating 20% decrease to the company's bottom line. At least EPS has managed not to go completely backwards from three years ago in aggregate, thanks to the earlier period of growth. Therefore, it's fair to say that earnings growth has been inconsistent recently for the company.

Weighing that recent medium-term earnings trajectory against the broader market's one-year forecast for expansion of 41% shows it's noticeably less attractive on an annualised basis.

In light of this, it's understandable that Nanjing Port's P/E sits below the majority of other companies. Apparently many shareholders weren't comfortable holding on to something they believe will continue to trail the bourse.

What We Can Learn From Nanjing Port's P/E?

Nanjing Port's recently weak share price has pulled its P/E below most other companies. 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 Nanjing Port maintains its low P/E on the weakness of its recent three-year growth being lower than the wider market forecast, as expected. At this stage investors feel the potential for an improvement in earnings isn't great enough to justify a higher P/E ratio. If recent medium-term earnings trends continue, it's hard to see the share price rising strongly in the near future under these circumstances.

Don't forget that there may be other risks. For instance, we've identified 2 warning signs for Nanjing Port (1 doesn't sit too well with us) you should be aware of.

Of course, you might also be able to find a better stock than Nanjing Port. 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.