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The Bank of Japan said Tuesday it made 11 sets of corrections to its statistics in less than three weeks during a bank-wide data review — and it expects to make more.

The central bank has discreetly corrected the data on its Web site, and adjusted figures bear a footnote instructing concerned parties to call the BOJ for details. The errors have so far been “minor” and do not require official announcements, officials said.

The BOJ announced Tuesday that it discovered miscalculations had been made involving the average outstanding reserves kept by private-sector banks at the BOJ over the past five years.

The numbers did not reflect mergers among financial institutions, the BOJ said. There was also one case of a number having been input incorrectly.

“There is absolutely no way these errors could impact monetary policy decisions,” claimed Yoshiki Tanji, director head of the Planning and Coordination Division’s operations department.

The mistakes may affect scholars “who examine numbers over long periods of time,” but few else, he said.

Some of the miscalculations were first discovered in August 2001, but the BOJ failed to find other errors made in the same way until this month. As the mistakes were due to human oversight and clerical errors, no official will be punished.

Tanji said that when deciding on monetary policy, the BOJ’s Policy Board looks at only final figures, which were unaffected by the errors. For over two years, the BOJ’s monetary policy has targeted specific figures for the outstanding balances in private financial institutions’ current accounts, which include reserves.

The BOJ last month began combing through its records to weed out mistakes, after it found errors in its tally of outstanding commercial paper. The slip-up went unreported until July.

The BOJ will reveal full details of its findings in October, it said.

Until then, market players will have to periodically check the central bank’s home page to make sure their analyses are based on the correct numbers.