A coalition of institutional investors including the California Public Employees' Retirement System is calling on a U.S. regulator not to delay the rule for companies to disclose the pay gap between their chief executive officers and rank-and-file workers.

The disclosure would help shareholders assess companies in their portfolios, investors representing $2.5 trillion in assets wrote in a letter Wednesday to Michael Piwowar, acting chairman of the Securities and Exchange Commission. Jay Clayton, who was picked by the Trump administration to serve as chairman, is scheduled to appear Thursday before the Senate Banking Committee for a hearing on his nomination.

"The SEC's pay ratio disclosure rule is thoughtful, balanced and carefully crafted," the letter said. "Delaying the implementation of this rule will do a huge disservice to investors."