Monetary Base YoY

The Monetary Base is currency supplied directly by the Bank of Japan (Japan's central bank) across Japan nationwide. It equals banknotes in circulation (cash issued by the Bank), plus coins in circulation, plus current account balances (deposits financial institutions hold at the Bank). It is a census-like aggregate from the Bank's own books, not a survey and not the money stock (broader money held by the public). Data run from January 1970 for monthly averages and July 1996 for end-of-period levels, with breaks in March/April 1981 and May 2000.

The Bank of Japan publishes Monetary Base Statistics monthly for Japan nationwide. Each release covers 1 reference month with 2 level types: monthly average amounts outstanding and end-of-period amounts. It appears on the 2nd business day of the next month around 8:50 Japan Standard Time. Delays from system problems or other unexpected disruption appear on the Bank's website.

Each 1-page PDF in Japanese and English shows year-earlier changes and levels in 100 million yen. Seasonally adjusted data are revised each February from the start, with errors fixed at once and retroactively. End-of-period levels joined the release with the May 2013 release, and a long-term time-series file sits on the same page.

Headline moves come mainly from current balances, which reflect policy liquidity.

• Banknotes in Circulation: banknotes issued by the Bank, including vault cash held by financial institutions.
• Coins in Circulation: coins in circulation, including holdings of financial institutions, the smallest and slowest leg.
• Current Account Balances: deposits financial institutions hold at the Bank, including tanshi companies and securities firms, capturing policy-driven liquidity.
• Reserve Balances: a non-additive memo part of current balances that counts as reserves, with the last 2 months preliminary.

The September 2025 release, published October 2, 2025, showed Monetary Base down 6.2% from 1 year earlier, after a 4.1% drop in August 2025. Current Account Balances fell 7.1%, while banknotes fell 2.1%, coins 1.4% and reserve balances 5.5%. Average levels were 6,281,080 in 100 million yen, split into 1,169,576 for banknotes, 46,320 for coins and 5,065,184 for current balances. End-of-period levels were 6,233,317, split into 1,166,246 for banknotes, 46,303 for coins and 5,020,768 for current balances. The seasonally adjusted annualized pace was down 23.5% for September, versus down 2.1% for August, far steeper than the yearly pace.

1. Level: Monetary Base equals banknotes plus coins plus current account balances, as a straight yen sum with no weights.
2. Yearly change: headline YoY equals (current monthly average minus average 12 months earlier) divided by that earlier average, times 100. For example, September 2025 averaged 6,281,080 (in 100 million yen) across 1,169,576 plus 46,320 plus 5,065,184, implying about 6,696,250 in September 2024 for down 6.2%.
3. Adjusted short pace: column (a) shows seasonally adjusted annualized change from the previous period.
4. Smoothing method: X-12-ARIMA version 0.3 uses a log transform for every series, with models reselected each year. Regressors cover rate-change months, coin and postal events, market operations and easing programs.
5. Reserve adjustment: adjusted reserves equal the month's reserve balances times the base-period rate over the comparison rate. The base period is the month after the latest rate change, November 1991.
6. Old and new basis: the new basis since April 1981 sums banknotes, coins and current balances. The old basis through March 1981 used reserve balances instead, and the May 2000 switch reached back to April 1997. It switched because deposits at institutions outside the reserve system move with markets, so current balances show supplied currency better.