The United States Oil Fund (NYSEArca: USO), which tracks West Texas Intermediate crude oil futures, fell again Monday, bringing its year-to-date loss to almost 48 percent. That put the widely followed oil exchange traded fund into the all-time low club, but oil’s struggles have not prevented USO from being a prolific gatherer of new assets this year.

Earlier this month, crude oil prices fell to their lowest levels since early 2009 after OPEC’s meeting ended without an agreement to lower production, Reuters reports. OPEC has been fueling a global supply glut in an attempt to maintain market share and squeeze out high-cost oil producers, such as the nascent shale industry in the U.S.

OPEC has kept up production to pressure high-cost rivals, such as the developing U.S. shale oil producers. The International Energy Agency expects it will take several years before OPEC can effectively price out high-cost producers. [Oil ETFs Face World-Record Supply Glut]

There are reasons for investors to be cautious with volatile energy ETFs. Moreover, if oil prices falls to new lows and the shale industry is unable to turn a profit, the highly leveraged industry may find it harder to repay debt obligations. The IEA said the “massive cushion has inflated” on record supplies from Iraq, Russia and Saudi Arabia.

Yet despite that need for caution, USO has seen plenty of new assets flow into it this year.

“But instead, a wide range of investors collectively spent about $24 billion over the past 18 months trying–and failing–to call a bottom in oil. Never in the history of exchange-traded funds has one particular category drawn so much money from investors trying to play a rebound. Of course, not all this money is gone (yet), although certainly a lot of it has evaporated along with the price of crude,” reports Eric Balchunas for Bloomberg.