On July 27, the Asahi Shimbun reported that the Bank of Japan had overestimated the value of mutual funds being held by individuals by about 30 percent. Every three months the BOJ publishes statistics called shikin junkan tōkei that cover the financial assets of households and businesses, and as of December 2017 the value of mutual funds held by households was estimated to be ¥109 trillion. However, in the report that came out in June, this number had dropped to ¥76 trillion, a difference of ¥33 trillion. That's a pretty big discrepancy.
The BOJ said the change was not due to a "mistake," but rather was "part of the work of revising" the statistics. According to the Asahi, the securities industry was dismayed by the news, since they had thought that the number of people buying mutual funds had been going up steadily since 2011, but really it has been dropping since 2015. Prior to the correction in June, it was believed that investment trusts accounted for 5.8 percent of individual asset holdings in Japan, but it turns out it is only 4.1 percent.
The chairman of the Investment Trusts Association told the newspaper that the revision was particularly disconcerting because of the importance of getting people to "create their own (investment) portfolios," while the head of the Japan Securities Dealers Association said that securities companies use the BOJ statistics to explain and sell their products, and if those numbers are wrong they will lose the public's trust.