Citigroup Inc. offered an uncharacteristically blunt assessment of the pay gap between men and women in its global workforce Jan. 16, revealing that female employees earn 29 percent less than men do.

The disclosure— a comparison of median total compensation—offers a more complete picture of pay, compared with the figures Citigroup and other big banks released last year under pressure from shareholders in the U.S. and regulators in the U.K.

The bank also reported that, among its U.S. employees, people...