Washington | Two years ago, Janet Yellen co-signed a letter to Treasury Secretary Steven Mnuchin urging him not to move forward with plans to relax oversight of big financial firms, warning that doing so could threaten the stability of America's financial system.

The plea by Yellen, who was joined by Ben Bernanke, another former Fed chair, and former Treasury secretaries Jacob Lew and Timothy Geithner, went unheeded.