Slow policy responses to the formation of the credit bubble in the US and UK exacerbated the troubles created by excessive risk-taking, said Hirohide Yamaguchi, one the two deputy governors of the Bank of Japan, in late November.

"One reason for that was the difficulty policy authorities faced in identifying the location and the size of risks, due to the expansion of so-called shadow banking by insurance firms, monoline companies and hedge funds," he told a retail finance conference in Tokyo.