In the committee stages, the majority - or more precisely the median - vote was implemented once all committee members had entered a vote into their respective computers. Participants were told nothing at the start of the experiment about the structure of the economic model with which they were playing, or the disturbances that it was subject to, other than that a structural change occurred at some point during each play of the game. In short, they were operating - much like real-life monetary policy makers - in uncertain conditions, doing their best to identify the shocks that hit the economy and offsetting their impact by adjusting the short-term interest rate. To quantify their performance, players were scored according to their ability to keep inflation close to a pre-specified target and to minimise output fluctuations, and were paid a modest amount for doing so. Chart 1 shows the pattern of average scores over the different stages of the game. Three features are striking: (i)  The significant upward trend in the results. Players clearly learned how to play the game as time went on. (ii)  The large upward movement in scores when players moved to committee decision-making. (iii)  The large downward move in scores when participants returned to playing as individuals. These results support the idea that committee decisions represent a significant improvement over those of the individuals that comprise them. What might account for these results? The Blinder and Morgan and Bank studies suggest two main reasons.
The mandate: price stability The Eurosystem has been entrusted with a very clear mandate by the European treaties;1 its primary objective is to “maintain price stability”, in other words to avoid prolonged periods of excessive inflation – as seen in Germany after World Wars I and II – or deflation – seen following the crisis of 1929 –, which have consistently negative effects on the economy. Some observers still advocate a “dual mandate” to target both inflation and growth or full employment, as is the case with the US Federal Reserve, for example. This would have been politically unattainable given the traumatic history of inflation in some European countries. Besides, let me recall two elements: price stability is to be maintained “over the medium term”. As stressed inter alia by F. Smets, there is an “equivalence between the length of the policy horizon and the weight on output gap stabilisation”,2 and hence employment. as stated by the treaty, "without prejudice to the objective of price stability”, the Eurosystem should support “the general economic policies in the Union” Let me add that the more precise and focused the mandate, the more accountable the ECB can and must be. Yet, those who advocate a broader mandate are often the same people who quite inconsistently are quick to criticise the lack of accountability of the ECB. In 1998, the ECB established a quantitative definition of price stability that it went on to clarify in 2003: to maintain inflation rates below, but close to, 2% over the medium term.