Since Governor Haruhiko Kuroda took office in March 2013, the Bank of Japan (BoJ) has been the most aggressively expansionary advanced-economy central bank. Its announcement last month of a “new framework for strengthening monetary easing”—coming only six months after introducing negative policy rates—distances it even further from the pack.

That a central bank is willing to assess its performance transparently and to consider new approaches to achieving its key goals is something we have come to expect. While it’s much too early to tell whether the latest BoJ innovations will be more successful, there is reason to be skeptical. No less important, the new approach involves risks to the central bank and to financial market stability that may not be fully appreciated. Given the difficulties that other advanced-economy central banks seem to be having in raising inflation and inflation expectations, how the BoJ fares is of interest far beyond Japan.