The Federal Reserve is under pressure. Whenever its chair Janet Yellen appears before US lawmakers she fields questions on whether the Fed has become too powerful, whether it should be made more accountable and whether the post-crisis reforms it has helped advance will blow up in its face. The line of attack differs from one Congressman to another.

Dealing with these inquiries is a drain on the Fed’s resources, at a time when it is also facing intense scrutiny from home and abroad as it prepares