What's happening: Shares of natural gas refueling leader Clean Energy Fuels Corp (NASDAQ:CLNE) are down more than 15% as of this writing. It's been a seriously up-and-down year for the company's stock so far:

CLNE Chart

CLNE data by YCharts.

Why it's happening: In short, yesterday's earnings report apparently didn't make Mr. Market happy, as the company fell short of Wall Street analyst estimates for revenue and earnings. 

But even with a "miss" based on these traditional measures, the company's business continues to strengthen, with falling operating costs and increasing margins as fuel sales continue to grow at double-digit rates. If you separate out the more cyclical results of the station construction and compression equipment businesses, fuel sales revenue was up about 10% from last year, even with fuel prices down about $0.10 per gallon, while the company maintained relatively strong margins-per-gallon of $0.27 even with the price decrease.

In short, the earnings report was much better than how the market seems to be responding today, and the company's financial performance in several key metrics improved. For more, check out the full earnings write-up here