OPEC Cuts Fail to Arrest Oil's Slide

On Wednesday, the Organization of Petroleum Exporting Countries announced a crude oil production cut of 2.46 million barrels per day starting Jan. 1, targeting a return to $75-per-barrel oil. World oil markets were unimpressed, continuing to sell off.

Oil stockpiles in Cushing, Okla., jumped 21% to 27.5 million barrels in one week, the largest volume increase since May 2007. The facility could reach full capacity in a few weeks, according to Barclays Capital analyst Paul Horsnell.

At Thursday's closing spot price of $36.22 per barrel, West Texas Intermediate Cushing Crude oil has tumbled 24.5% in a week and 75.2% since its July 2008 peak of $146.30 a barrel.

West Texas Intermediate Crude Crashes Below $40 Bloomberg

The worst-performing fund for the five trading days ending Thursday, Dec. 18, is Morgan Stanley Natural Resource Development Securities (NREAX Quote), which has lost 26.79% on a portfolio heavy in stocks like Chevron (CVX Quote), Exxon Mobil (XOM Quote) and Schlumberger (SLB Quote).