As has been widely documented, energy is the worst-performing sector in the S&P 500 this year, but some of the sector’s exchange traded funds are taking oil’s decline worse than others.

For example, the VanEck Vectors Oil Service ETF (NYSEArca: OIH), the largest oil services exchange traded fund, is lower by 18.7% year-to-date. Rivals to OIH include the SPDR Oil & Gas Equipment & Services ETF (NYSEArca: XES), iShares U.S. Oil Equipment & Services ETF (NYSEArca: IEZ) and the PowerShares Dyanmic Oil & Gas Services Portfolio (NYSEArca: PXJ). Those ETFs are stumbling as well.

Exploration and production ETFs are also being taken to task. Just look at the SPDR S&P Oil & Gas Exploration & Production ETF (NYSEArca: XOP), which is lower by 16% year-to-date.

The Direxion Daily S&P Oil & Gas Exploration & Production Bear Shares (NYSEArca: DRIP) takes the -3x, or -300%, daily performance of the S&P Oil & Gas Exploration & Production Select Industry Index, the same index tracked by XOP.

Given the historical sensitivity of exploration and production names to oil prices, it would stand to reason that lower oil output would benefit the industry. While the Organization of Petroleum Exporting Countries (OPEC) has moved to trim output, U.S. shale producers are boosting production as highlighted by the rising rig count in the U.S.

The energy sector could be near a bottom, “but we’re going to see this very choppy trading maybe over the coming months, the coming quarter, even the coming years. And I think in the process, the energy sector is going to underperform versus a rising S&P 500, and that equities as a whole will do better than the energy sector,” said Ari Wald, Oppenheimer head of technical analysis, in a CNBC interview.

OIH tracks the 25 largest oil services companies in the space. Both XES and IEZ track a slightly broader 37 components, but XES follows a more equal-weight indexing methodology that favors midsized companies while IEZ reflects a traditional market cap-weighted indexing methodology. Lastly, PXJ follows a fundamentally weighted index, which selects stocks based on price momentum, earnings momentum, quality, management action, and value.

“The bigger problem for oil is in the United States, however, where oil production has boomed. U.S. shale production is set to rise for the sixth straight month in June, sending production to its highest level since May 2015, according to a recent Energy Information Administration report,” according to CNBC.

For more information on the energy sector, visit our energy category.