TOKYO — After insisting for more than a year that its aggressive monetary policy was sufficient to revive Japan’s economy and end deflation, the Bank of Japan on Friday unexpectedly announced that it would increase the amount of money it pumped into the country’s financial markets by buying larger quantities of government debt.

The central bank surprised analysts and investors by expanding its program of bond-buying — an initiative similar to the stimulus just ended by the Federal Reserve in the United States — to increase Japan’s monetary base by 80 trillion yen a year, or $734 billion, up from a previous range of ¥60 trillion to ¥70 trillion.  Read more