'If you look at previous times in US history when bond yields were this low, the returns have been quite poor. Bonds now have many elements of a bubble. We're at the end of the debt super cycle. First we had a large banking crisis. The next step is a large sovereign crisis. This means that government bonds are a pretty bad bet over a five to ten year period,' said Jonathan Tepper, partner and chief editor of Variant Perception, an economic research boutique.