Companies will have to provide investors with a ratio showing how the median pay of their workforce squares with their chief executive officers’ compensation, according to new rules slated for adoption by U.S. securities regulators on Wednesday. The SEC has been under mounting pressure by Democrats, like Massachusetts Senator Elizabeth Warren and unions, who support the rule and have lamented delays in its adoption. The measure was tucked into the 2010 Dodd-Frank law amid concerns about the growing disparity between compensation for chief executives and their corporate workers.