Shanghai Serum Bio-Technology Co., Ltd. (SHSE:688163) shares have continued their recent momentum with a 44% gain in the last month alone. Taking a wider view, although not as strong as the last month, the full year gain of 13% is also fairly reasonable.

Since its price has surged higher, given close to half the companies in China have price-to-earnings ratios (or "P/E's") below 33x, you may consider Shanghai Serum Bio-Technology as a stock to avoid entirely with its 53.6x P/E ratio. Although, it's not wise to just take the P/E at face value as there may be an explanation why it's so lofty.

For instance, Shanghai Serum Bio-Technology's receding earnings in recent times would have to be some food for thought. One possibility is that the P/E is high because investors think the company will still do enough to outperform the broader market in the near future. You'd really hope so, otherwise you're paying a pretty hefty price for no particular reason.

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

Shanghai Serum Bio-Technology's P/E ratio would be typical for a company that's expected to deliver very strong growth, and importantly, perform much better than the market.

If we review the last year of earnings, dishearteningly the company's profits fell to the tune of 27%. As a result, earnings from three years ago have also fallen 53% overall. Accordingly, shareholders would have felt downbeat about the medium-term rates of earnings growth.

In contrast to the company, the rest of the market is expected to grow by 37% over the next year, which really puts the company's recent medium-term earnings decline into perspective.

In light of this, it's alarming that Shanghai Serum Bio-Technology's P/E sits above the majority of other companies. It seems most investors are ignoring the recent poor growth rate and are hoping for a turnaround in the company's business prospects. There's a very good chance existing shareholders are setting themselves up for future disappointment if the P/E falls to levels more in line with the recent negative growth rates.

The Key Takeaway

Shares in Shanghai Serum Bio-Technology have built up some good momentum lately, which has really inflated its P/E. It's argued the price-to-earnings ratio is an inferior measure of value within certain industries, but it can be a powerful business sentiment indicator.

Our examination of Shanghai Serum Bio-Technology revealed its shrinking earnings over the medium-term aren't impacting its high P/E anywhere near as much as we would have predicted, given the market is set to grow. When we see earnings heading backwards and underperforming the market forecasts, we suspect the share price is at risk of declining, sending the high P/E lower. If recent medium-term earnings trends continue, it will place shareholders' investments at significant risk and potential investors in danger of paying an excessive premium.

Having said that, be aware Shanghai Serum Bio-Technology is showing 3 warning signs in our investment analysis, and 1 of those is a bit concerning.

If P/E ratios interest you, you may wish to see this free collection of other companies with strong earnings growth and low P/E ratios.

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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.