Those holding Nanfang Ventilator Co., Ltd. (SZSE:300004) shares would be relieved that the share price has rebounded 25% in the last thirty days, but it needs to keep going to repair the recent damage it has caused to investor portfolios. Unfortunately, the gains of the last month did little to right the losses of the last year with the stock still down 13% over that time.

After such a large jump in price, given around half the companies in China's Building industry have price-to-sales ratios (or "P/S") below 1.8x, you may consider Nanfang Ventilator as a stock to avoid entirely with its 6.3x P/S ratio. Although, it's not wise to just take the P/S at face value as there may be an explanation why it's so lofty.

How Nanfang Ventilator Has Been Performing

As an illustration, revenue has deteriorated at Nanfang Ventilator over the last year, which is not ideal at all. Perhaps the market believes the company can do enough to outperform the rest of the industry in the near future, which is keeping the P/S ratio high. However, if this isn't the case, investors might get caught out paying too much for the stock.

Is There Enough Revenue Growth Forecasted For Nanfang Ventilator?

Nanfang Ventilator's P/S ratio would be typical for a company that's expected to deliver very strong growth, and importantly, perform much better than the industry.

Taking a look back first, the company's revenue growth last year wasn't something to get excited about as it posted a disappointing decline of 10%. As a result, revenue from three years ago have also fallen 48% overall. Accordingly, shareholders would have felt downbeat about the medium-term rates of revenue growth.

Weighing that medium-term revenue trajectory against the broader industry's one-year forecast for expansion of 25% shows it's an unpleasant look.

With this in mind, we find it worrying that Nanfang Ventilator's P/S exceeds that of its industry peers. Apparently many investors in the company are way more bullish than recent times would indicate and aren't willing to let go of their stock at any price. There's a very good chance existing shareholders are setting themselves up for future disappointment if the P/S falls to levels more in line with the recent negative growth rates.

The Bottom Line On Nanfang Ventilator's P/S

The strong share price surge has lead to Nanfang Ventilator's P/S soaring as well. Using the price-to-sales 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.

Our examination of Nanfang Ventilator revealed its shrinking revenue over the medium-term isn't resulting in a P/S as low as we expected, given the industry is set to grow. When we see revenue heading backwards and underperforming the industry forecasts, we feel the possibility of the share price declining is very real, bringing the P/S back into the realm of reasonability. If recent medium-term revenue trends continue, it will place shareholders' investments at significant risk and potential investors in danger of paying an excessive premium.

It's always necessary to consider the ever-present spectre of investment risk. We've identified 1 warning sign with Nanfang Ventilator, and understanding should be part of your investment process.

If companies with solid past earnings growth is up your alley, 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.