The lack of clarity from the Federal Reserve (Fed) on when it will begin to withdraw stimulus to deal with the pandemic, at the same time as the U.S. bond yield continues to rally after months of steady increases - in the first days of January it has surpassed 1%, a level not seen since the beginning of the pandemic - has made many in the financial world resurrect the ghost of the 2013 'taper tantrum' as a real possibility for this 2021.