What: Shares of jeweler Tiffany & Co. (TIF) fell 13.2% in May, according to data provided by S&P Global Market Intelligence, after the company reported weak first-quarter earnings.

So what: Revenue fell 7.4% to $891.3 million, which fell well short of analysts' estimates of $924.1 million. On the bottom line, net income fell 16.6% to $87.5 million, or $0.69 per share. On an adjusted basis, earnings were $0.64 per share, four cents short of estimates. 

Sales in the Americas fell 9% and Asia-Pacific dropped 8%, showing how much weakness there is globally in the luxury jewelry market. And management is expecting full-year earnings per share to decline a mid-single-digit percentage from a year ago, so the pressure is expected to continue.

Now what: Tiffany has been a big beneficiary of the global recovery over the past six years and the growth of the Asian middle and upper class over that time. But with global economic growth slowing, the company's sales are under pressure as well. But investors with a long-term focus should recognize that the Tiffany brand is still strong, and with shares trading at 16 times forward earnings estimates it could be a good time to buy shares at a value.