Japan’s monetary base in September rose 21.4 percent from a year earlier to 85.747 trillion yen, up for the 20th straight month, the Bank of Japan said Wednesday.

The monetary base — cash in circulation plus money held by banks at the central bank — rose 26.1 percent in August.

The September increase marked a 13th consecutive double-digit ascent.

The balance of banks’ current accounts at the BOJ rose 88.1 percent in the reporting month to 15.205 trillion yen, the central bank said.

The balance rose 171.9 percent the previous month.

The monetary base has been growing quickly since March 2001, when the BOJ adopted a quantitative monetary easing policy, injecting funds into the banking system in hopes of stemming deflation.

The central bank has maintained a policy of providing funds flexibly, regardless of its 10 trillion yen to 15 trillion yen target for current account deposits held at the BOJ by commercial banks.