The return of inflation

For a quarter of a century, the western world has enjoyed a macroeconomic environment characterized by low and stable inflation. Over the last two years, this benign state has dramatically changed. In America and Europe, inflation has resurged with unexpected vigor. Treated at first by central banks and most of their observers as a mere temporary aberration, which would soon fade again without much need for action, it has since assumed a virulence which has forced central banks to tighten their policies much more forcefully than was initially expected. How did all this come about? How are central banks and their monetary policies to be judged?