It is because the Fed has, throughout the last 18 years, been very highly credible that remarkable successes have been achieved on price stability, even without what I would consider as a precondition for anchoring inflationary expectations: a quantitative definition of price stability.
In all difficult episodes and crises the credibility of the Fed has been decisive in the effectiveness of its handling of the situation. In the case of the Governing Council of the ECB I have explained that our credibility has enabled us to regain full control of inflationary expectations with remarkable efficiency over the last two years.