It’s also unclear whether the changing priorities will be reflected in firms’ compensation plans. Roughly two-thirds of CEO pay for those in the S&P 500 comes in the form of stock awards. Share performance is among the most common metrics to determine payouts, appearing in about half of pay plans for the CEOs of the 181 companies that signed the pledge, according to data compiled by Bloomberg.

At S&P 500 firms, the average ratio between the CEO’s compensation and that of the median worker is about 280-to-1, the data shows.

“The rising income inequality between executives and employees won’t be meaningfully eradicated by compensating employees fairly unless executives are willing to be paid less,” Jackson said.

Missing Firms

Absent from the 181 signatories were the leaders of Roundtable members Wells Fargo & Co., State Farm, Parker-Hannifin Corp., NextEra Energy Inc., Kaiser Permanente, General Electric Co., Blackstone Group Inc. and Alcoa Inc.

Representatives for Kaiser and State Farm both said the firms support the pledge but elected not to sign it because they don’t have shareholders. A GE spokeswoman said that CEO Larry Culp consistently makes public statements about focusing on creating value for stakeholders such as customers, employees and investors, but declined to comment further. Wells Fargo wasn’t invited to sign the pledge because its current chief executive serves on an interim basis, a spokeswoman said.

The other companies didn’t respond to requests seeking comment.

The adherence to shareholder-first model is widely traced back to a New York Times column written by Nobel laureate Milton Friedman in 1970, in which he spurned corporate leaders who “declaim that business is not concerned ‘merely’ with profit,” but also things like avoiding pollution or “whatever else may be the catchwords of the contemporary crop of reformers.”

‘Frustrating Thing’

The idea of maximizing shareholder returns took hold in executive suites and academic circles over the following decades, with some even claiming that companies have a legal duty to do so.