Japan's Monetary Base Shrinks Faster Than Expected in August

Japan's monetary base shrunk at an accelerated pace in August, according to Bank of Japan data. The monetary base, which includes cash in circulation and bank deposits held at the BoJ, fell by 15.7% from a year earlier - its steepest drop since September 2024.

The contraction was driven primarily by a decline in bank money parked at the BoJ, with current account balances sinking 18.9% and reserve balances falling 18.0%. This represents a sharper decline than the prior month, suggesting that households are not ditching cash but rather the pool of settlement balances inside the banking system is shrinking.

The impact on short-term rates could be significant. When reserves fall quickly, banks have less cash to settle payments and often lean more on overnight lending and repurchase agreement (repo) markets, where borrowing against collateral can push up very short-term borrowing costs.