Twelve countries are members of the Organization of Petroleum Countries (OPEC), the cartel that accounts for about 40% of global oil output and looms large when it comes to setting prices of the commodity.

Three OPEC member nations – Nigeria, Qatar and the United Arab Emirates – are represented in the world of exchange traded funds by three U.S.-listed, single-country funds. Not surprisingly, these ETFs have been punished as oil prices have plunged in recent weeks.

Over the past month, the United States Oil Fund (NYSEArca: USO) and the United States Brent Oil Fund (NYSEArca: BNO) are down an average of 11.2% over the past month, a decline that has stoked similar treatment of ETFs such as the Global X MSCI Nigeria ETF (NYSEArca: NGE) and the iShares MSCI Qatar Capped ETF (NasdaqGM: QAT).

NGE and QAT, the lone single-country ETFs devoted to Nigeria and Qatar, have lost 9.9% and 8.2% over the past month. Underscoring the sensitivity of OPEC nations’ equity markets to oil prices, NGE has been performed slightly worse in recent weeks than the iShares MSCI Canada ETF (NYSEArca: EWC), a relevant comparison because Canada is home to, by some estimates, the largest non-OPEC oil reserves in the world. [Falling Oil Pressures Canada ETFs]

NGE has tumbled 15.2% this year as rising U.S. oil output has trimmed the world’s largest oil importer’s needs for Nigerian oil. Both the U.S. and Nigeria produce highly desirable light sweet crude. Nigeria vies with fellow OPEC member Angola for the top spot among Africa’s oil producing nations.

NGE’s struggles this year compare with a 6.9% gain for the iShares MSCI Frontier 100 ETF (NYSEArca: FM), an ETF in which Nigeria is the second-largest country weight at 13.3%. [Nigeria ETF Benefits From Frontier Index Changes]