(AP Photo/Dake Kang) Fed Chair Janet Yellen speaks at an economics conference on September 26, 2017, in Cleveland. R ecent reports indicate that President Trump will not re-appoint Janet Yellen as the chair of the Federal Reserve’s Board of Governors. Instead, the reports indicate that he will appoint a current member of the board, Jerome Powell. Choosing to pass over Yellen is an obvious mistake. Yellen is a world-recognized expert in macroeconomics and has enormous experience as a policymaker. Her performance as Fed chair has been widely and correctly praised . She takes the Fed’s mandate to maximize employment seriously and is data-driven. To be clear, I think she’s made a misstep or two in specific interest rate decisions, but with Yellen, those arguing with economic data have a real chance to be heard. Her recent speech at the Federal Reserve conference in Jackson Hole, Wyoming, also provided an admirable signal that she continued to take the Fed’s role as chief financial-sector...