In the struggling energy sector, the worst-performing sector in the S&P 500 this year, refining stocks have stood out. Since it came to market in August, the Market Vectors Oil Refiners ETF (NYSEArca: CRAK) has posted a gain of 1%, better than triple the gain notched by the Energy Select Sector SPDR (NYSE: XLE) over the same period.

CRAK tries to reflect the performance of the Market Vectors Global Oil Refiners Index, a modified market cap-weighted index that follows the largest and most liquid companies in the global oil refining industry.

The oil refinery business may benefit from lower crude oil prices, or lower input costs. The price of finished products such as gasoline, diesel and fuel oil can affect a refinery’s profitability. Consequently, the difference between the cost of crude oil and the price of the products, or so-called crack spread, is a common indicator of the potential profits.

“Many refiners were spun out of integrated oil-exploration companies in the past four years, a process that has also helped to unlock value in the group. Marathon Petroleum (MPC), for instance, was spun out of Marathon Oil (MRO) in 2011, and Phillips 66 (PSX) was set loose from ConocoPhillips (COP) in 2012. (See table nearby for a more complete list of refiner-company spinoffs.) These and other refinery operators have been the subject of bullish stories in Barron’s in recent years,” reports Vito Racanelli for Barron’s.

“Refiners have been the lone bright spot in the energy sector during the past year, handily outperforming every other subsector,” writes Allen Good is a senior equity analyst for Morningstar. “While oil prices have deteriorated, refining margins have improved, thanks to strength in gasoline margins due to key refinery outages and strong demand.”