Without meaningful changes to the way oil companies operate, energy stocks and sector-related exchange traded funds may continue to meander through a slow growth environment.

Year-to-date, the Energy Select Sector SPDR (NYSEArca: XLE) fell 2.6%, Vanguard Energy ETF (NYSEArca: VDE) dropped 3.0% and iShares U.S. Energy ETF (NYSEArca: IYE) decreased 3.0%.

“The days of Big Oil are by no means over, but today’s environment requires a change to the model,” Morgan Stanley and The Boston Consulting Group said, reports Javier Blas for Bloomberg.

The warning comes as investors try to find value in big oil companies like Exxon Mobil (NYSE: XOM) and Chevron (NYSE: CVX) while oil prices hover around $60 per barrel, compared to $100 per barrel a year ago. West Texas Intermediate crude oil futures were trading around $58.3 per barrel Monday while Brent crude oil futures were at $62.0 per barrel.

The pressure on oil prices will not likely let up any time soon. Despite signs that the global economy is using up more oil, producers are still pumping out two million barrels of crude oil above demand per day, reports Georgi Kantchev fo the Wall Street Journal.

U.S. production has not slowed much, the Organization of the Petroleum Exporting Countries has raised output, and the market anticipates more supply from Iran if a nuclear deal is passed.

Even before the plunge in oil prices, large oil producers were experiencing lower returns on capital and some were struggling to meet investment and dividend demands.