Fed Chairman Jerome Powell will speak Thursday during a virtual version of the Fed’s annual Jackson Hole, Wyoming, conference. He is expected to outline what could be the central bank’s most active efforts ever to spur inflation back to a healthy level. “Average inflation” targeting means the Fed will allow inflation to run higher than normal for a period of time. The effort will be the reverse of former Fed Chairman Paul Volcker’s rate hikes instituted to quash inflation in the 1980s. History will remember Paul Volcker and Jerome Powell as standing on the opposite ends of the inflation canyon,...