Even women who beat the odds and rise to the c-suite face a familiar foe in the corner office -- the pay gap.

Although female chief executive officers at the largest U.S. companies now earn as much or more than their male counterparts, women just one rung down on the corporate ladder often earn less than their male colleagues, according to an analysis of 2018 proxy filings by ISS Analytics, a unit of Institutional Shareholder Services.

“When you start to look below that top chair, that’s where the disparity starts to creep in,” said John Roe, the head of ISS Analytics. “You start to see the subtle biases come out the further you get from the CEO chair.”

C-suite jobs tend to break down on gender lines, with women most likely to be the head of human resources, general counsel or chief administrative officers. Operational roles, like chief operating officer or chief financial officer, are more typically held by men. The median salary for an S&P 500 COO is twice that for heads of HR, according to pay consultant Mercer LLC.

Women CEOs earn 20 per cent more than men among S&P 100 companies, meaning the biggest companies pay the highest premium for women at the helm, Roe said. The pay is about even in the rest of the S&P 500 and smaller companies.

One level down, the occupational sorting means that even when women get a seat at the table, it’s not worth as much. For chief operating and financial officers, median compensation is around $4.7 million and $3.6 million, respectively, according to Mercer. In contrast, general counsel and chief human resources officers, which ISS says have the highest percentage of women, have median payouts of $2.5 million and $2.2 million, Mercer data shows.