Last week, for the first time in its history, Germany sold five-year bonds that guaranteed a negative yield. And Germany is not alone. Eurozone nations, including France, Belgium, Finland, Denmark, Switzerland, Netherlands, Sweden and Austria, have issued bonds with negative yields.

This means investors, as a reward for tying up their money for several years, will get less money back than they put in when the bonds mature.

Among the rationale for investors to accept a loss is that government bonds provide a safe haven in an uncertain economic future. And with banks trending toward negative interest rates (charging savers to hold their money) and bail-ins that permit seizure of deposits above the insured amounts, negative bond yields, rather than bank deposits, are the price paid for security.

Moreover, there are assumptions that in the current economic climate of deflation and weakening currencies, investors may get some protection should future deflation exceed the current negative bond yield.