Negative real rates of return

Systematically negative real rates of return are rare but possible.  This differs from unexpected negative real rates on debt instruments, due to earlier underestimations of inflation.  True negative real rates of return imply the economy cannot put resources to productive use.  Decay and deterioration rule.  Of course there must be storage costs for goods.  Otherwise people could hold those goods and receive a zero rate of return.  There must be price inflation, otherwise people could hold currency and receive a zero rate of return.

For examples, look to spoilage-vulnerable agricultural economies during times of war and siege.  I also believe they have negative real rates of return in Battlestar Galactica.  That is one reason why neither discretionary monetary nor fiscal policy will improve their lot.

Negative nominal rates of interest on money are harder to come by, but deteriorating paper or risk of theft could in principle do it.  You must prefer to lend out your money at negative return than to hold it at an even more negative return.  I have yet to see an example of this, not even on TV.