The issue is growth and its relationship with inflation. The question should therefore be couched as "What is the best rate of inflation for maximum growth?" If it happens to be the 2% thumbsuck of the ECB (and Bank of England), then fine. However in these times of crisis it seems an opportune time to provide a different answer to the question! Just make sure only one economist is asked, as the answer could well be as varied as the number of economists consulted.
The view of the ECB, however, appears not to understand what the question should be. It implicitly thinks that low inflation is the primary objective, with growth and employment secondary:
"To maintain price stability is the primary objective of the Eurosystem and of the single monetary policy for which it is responsible. This is laid down in the Treaty on the Functioning of the European Union, Article 127 (1).
Without prejudice to the objective of price stability", the Eurosystem shall also "support the general economic policies in the Union with a view to contributing to the achievement of the objectives of the Union". These include inter alia "full employment" and "balanced economic growth".
http://www.ecb.europa.eu/mopo/intro/objective/html/index.en.htmlSimilarly the Bank of England:
"The Bank’s monetary policy objective is to deliver price stability – low inflation – and, subject to that, to support the Government’s economic objectives including those for growth and employment."
http://www.bankofengland.co.uk/monetarypolicy/framework.htm