Sleep Number Corporation (NASDAQ:SNBR) shareholders will doubtless be very grateful to see the share price up 43% in the last month. But that is meagre solace in the face of the shocking decline over three years. Indeed, the share price is down a whopping 89% in the last three years. So we're relieved for long term holders to see a bit of uplift. But the more important question is whether the underlying business can justify a higher price still. While a drop like that is definitely a body blow, money isn't as important as health and happiness.

With the stock having lost 13% in the past week, it's worth taking a look at business performance and seeing if there's any red flags.

While the efficient markets hypothesis continues to be taught by some, it has been proven that markets are over-reactive dynamic systems, and investors are not always rational. By comparing earnings per share (EPS) and share price changes over time, we can get a feel for how investor attitudes to a company have morphed over time.

Sleep Number saw its share price decline over the three years in which its EPS also dropped, falling to a loss. Since the company has fallen to a loss making position, it's hard to compare the change in EPS with the share price change. But it's safe to say we'd generally expect the share price to be lower as a result!

You can see how EPS has changed over time in the image below (click on the chart to see the exact values).

We consider it positive that insiders have made significant purchases in the last year. Even so, future earnings will be far more important to whether current shareholders make money. It might be well worthwhile taking a look at our free report on Sleep Number's earnings, revenue and cash flow.

A Different Perspective

Sleep Number shareholders are down 49% for the year, but the market itself is up 31%. However, keep in mind that even the best stocks will sometimes underperform the market over a twelve month period. Unfortunately, last year's performance may indicate unresolved challenges, given that it was worse than the annualised loss of 11% over the last half decade. We realise that Baron Rothschild has said investors should "buy when there is blood on the streets", but we caution that investors should first be sure they are buying a high quality business. While it is well worth considering the different impacts that market conditions can have on the share price, there are other factors that are even more important. Take risks, for example - Sleep Number has 3 warning signs (and 2 which are a bit concerning) we think you should know about.

Sleep Number is not the only stock that insiders are buying. For those who like to find winning investments this free list of growing companies with recent insider purchasing, could be just the ticket.

Please note, the market returns quoted in this article reflect the market weighted average returns of stocks that currently trade on American exchanges.

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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.