Ferguson, who was vice chairman of the Federal Reserve's Board of Governors from 1999 to 2006, is among several Treasury secretary candidates.

According to the GAO, there has been a significant growth in market concentration for individual insurance plans.

"The reality is that race, unfortunately, in America still matters. I wish it were not an issue, but it is," said U.S. District Judge Reggie Walton, speaking as part of a National Judicial College panel.