In one of the day’s more puzzling developments, the Mexican peso tumbled on news that the head of the Mexican central bank, Augusten Carstens, who several years ago competed against Christine Lagarde for the top IMF post, announced he would unexpectedly stand down from his post next July. The term of the 58-year-old Carstens, who headed the central bank since 2010, was due to conclude at the end of 2021, which makes today’s announcement particularly surprising.