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<P>Fabio Busetti<SUP>a</SUP>, Lorenzo Forni<SUP>a</SUP>, Andrew Harvey<SUP>b</SUP>, and Fabrizio Venditti<SUP>a</SUP>
<H4>Abstract</H4>
<P>We study the convergence properties of inflation rates among the countries of the European Monetary Union over the period 1980-2004. Given the Maastricht agreements and the adoption of the single currency, the sample can be naturally split into two parts, before and after the birth of the euro. We study convergence in the first subsample by means of unit-root tests on inflation differentials, arguing that for testing absolute convergence, a power gain is achieved if the Dickey-Fuller regressions are run without an intercept term. We find evidence for the convergence hypothesis over the period 1980-97 and a clear indication of the important role played by the Exchange Rate Mechanism (ERM) in strengthening the convergence process. We then investigate whether the second subsample is characterized by stable inflation rates across the European countries. Using stationarity tests on inflation differentials, we find evidence of diverging behavior. In particular, we can statistically detect two separate clusters, or stability clubs: (i) a lower-inflation group that comprises Germany, France, Belgium, Austria, and Finland and (ii) a higher-inflation one with Spain, the Netherlands, Greece, Portugal, and Ireland. Italy appears to form a cluster of its own, standing between the other two. </P>