What happened

E-commerce giant Wayfair (W -2.94%) trailed the market last month as shares lost 11% compared to a 7% decline in the S&P 500, according to data provided by S&P Global Market Intelligence.

The decrease erased only a small portion of shareholders' recent returns, though, and the stock remains higher by over 50% so far in 2019.

A modern-appointed living room.

Image source: Getty Images.

So what

Wayfair announced first-quarter earnings results in early May that helped show why this is such a hard stock for investors to value. The home furnishings specialist continued to win market share, as it added millions of customers and saw sales jump 39% in the core U.S. market. However, soaring expenses, particularly in international geographies like Europe and Canada, generated hefty losses.

Now what

Wayfair is losing money at such a fast clip because management sees a big opportunity to establish a leadership position in places like the U.K. and continental Europe. There's good support for this bullish reading, including the fact that sales volumes and gross profitability trends are strong in the more mature U.S. segment.

Still, it will likely be at least another fiscal year before it's clear whether Wayfair can approach its long-term goal of sustainable profitability on a global basis. Until that key question is answered, the stock is likely to remain extremely volatile.