He said he had been involved in some high level discussions about alternatives to the bank's remit since delivering a speech in December in which he discussed targeting nominal GDP - a measure that takes into account inflation and growth.
This shortage manifests itself in the form of interest rates on Treasury securities that are near zero in nominal terms, and below zero when inflation is taken into account.
The results change a little whether you use nominal GDP per head (ie, just the plain numbers ) or PPP adjusted (to take account of different price levels) but the are a number of countries in Europe with higher GDP per capita than Germany.