In a presentation at the New York Stock Exchange this week, Doug Suttles, CEO of Encana Corp. (NYSE: ECA), spelt out the new reality for North American oil and gas producers. The industry had gone from “resource capture” to “value maximization” Suttles said.

This is a profound change. Since the shale oil revolution began in the late 2000s, management teams have mostly focused on growth at any cost and investors have mostly been prepared to back them.

In 2017, however, investor sentiment has shifted. Shareholders are less dazzled by the excitement of the shale boom and more interested in orthodox measures of success including returns on capital and cash generation.

For Encana, which produces gas and oil in the U.S. and Canada, the shift has prompted an effort to change the company’s culture.

“The same conversation we have with our investors, about creating value by delivering quality corporate returns, is the conversation we’re constantly having within the company,” Suttles said.

The whole shale industry is being pushed in the same direction. If companies fail to improve shareholder return, “investors will start to question what management is doing,” Stephen Trauber, global head of energy at Citigroup Inc. (NYSE: C), said.

For the past eight years, the U.S. exploration and production industry has outspent its cash flows in drilling costs, requiring a constant inflow of debt and equity financing to keep going. But the industry has given shareholders very little in return.

Even the biggest industry success stories, EOG Resources Inc. (NYSE: EOG) and Pioneer Natural Resources Co. (NYSE: PXD), have underperformed the index over the past five years, recording total shareholder returns of 74% and 35% respectively, compared to a 95% return for the S&P 500. Other leading exploration and production companies have left investors in the red. Continental Resources Inc. (NYSE: CLR) has reported a five-year loss for shareholder of 7%, and of 51% for Marathon Oil Corp. (NYSE: MRO).

Given those numbers, it is unsurprising that investor interest appears to have waned. U.S. exploration and production companies raised $34.3 billion from share sales in 2016, making it a record year, but just $5.7 billion in the first nine months of 2017, according to Dealogic.

Kevin Holt of Invesco Ltd. (NYSE: IVZ) is one of the fund managers arguing that the industry must change course. He has risen to the boards of a number of exploration and production companies, urging them to aim for lower growth rates and to focus on raising rates of return and free cash flow while reducing debt and equity issuance.

If they do not do that, he said, companies will carry on over-investing and over-producing, depressing oil and gas prices and continuing to lose money.

“It’s like the George Clooney movie, The Perfect Storm,” he said. “You realize it’s going to end badly if you continue like this.”

Another sign of the more demanding attitude among investors is a resurgence of shareholder activism. It is not a new phenomenon—there have been battles between investors and management at Chesapeake Energy Corp. (NYSE: CHK) and Hess Corp. (NYSE: HES), among others—but it is making a comeback, with shareholders challenging management at EQT Corp. (NYSE: EQT) and Energen (NYSE: EGN). Advisers say there are other companies where investors have started to exert pressure behind the scenes.

“Activists are targeting the sector because it is out of favor and they see potential gains,” David Rosewater, the head of shareholder activism defence at Morgan Stanley (NYSE: MS), said. “We see this trend continuing until shale companies can improve their returns and show production growth while living within cash flow.”

There was a significant move in September from Anadarko Petroleum Corp. (NYSE: APC), which said it would buy back $2.5 billion of shares. Markets rewarded it with a 7% share price rise, adding about $1.8 billion to the company’s market capitalization. The warm reception for a company returning cash to shareholders sent a signal that others were likely to follow, Holt said.

The pressure from investors for more discipline—a word used 17 times by Encana in its presentation—already seems to be having an effect. The number of active rigs in the U.S. drilling, the horizontal wells used for shale oil production, has been dropping since the beginning of August.

Paal Kibsgaard, CEO of Schlumberger (NYSE: SLB), told analysts on Oct. 20 that growth in activity in North America was slowing, as “the previous pursuit of production growth is now being balanced out with an equal focus on generating solid financial returns and operating within the cash flow.”

Jamaal Dardar, an analyst at Tudor Pickering Holt & Co., said just six months ago he would have expected U.S. oil and gas producers to go on outspending their cash flows into 2018 at least. He now expects that in 2018 the larger exploration and production companies will in aggregate earn positive free cash flow, after capital spending but before dividend payments. Many of the larger ones, including Anadarko, Apache Corp. (NYSE: APA) and Noble Energy Inc. (NYSE: NBL), are helped by the fact that they have international operations that do not demand the continual drilling needed for shale.

“Companies are saying, ‘We really need to live within our means’,” Dardar said. “And they are getting a lot of questions from investors saying, ‘Can you do the same as Anadarko? We’d like to see that sooner rather than later’.”

Smaller companies that find it harder to generate cash may end up being taken over, he added, as falling share prices start to make them look more attractive targets for larger groups.

U.S. oil production is still expected to rise in 2018, partly because of a backlog of wells that have been drilled, but not yet brought into production. It is on course to hit a new record above 10 million barrels a day at the end of 2018, according to the Energy Information Administration. But companies with more grandiose growth plans may be forced to temper their ambitions.

“We all like growth, but it must be profitable growth,” Holt said. “They might be able to grow at 5% or 10% per year, but not at 20%.”

If companies bow to that pressure from investors, it could work out very neatly. Slower oil production growth in the U.S. would help push crude prices higher, making it possible for the industry to deliver the returns that shareholders want.

But Citi’s Trauber warns the history of the oil industry shows it rarely delivers such tidy outcomes.

“We have been here before,” he said. “At times over the past 30 years, investors have demanded discipline from the industry. But then as soon as the oil price picks up again, they have forgotten all about it and the industry has rushed back to growth again.”