FX Intervention

Intervention can be unsterilized or sterilized — two terms worth knowing. Unsterilized intervention lets the transaction affect the domestic money supply: buying the home currency shrinks money in circulation, which tends to tighten financial conditions. Sterilized intervention offsets that effect with other transactions so the money supply stays unchanged, targeting only the exchange rate itself. Most developed-economy interventions are sterilized. The mechanics link directly to how central banks influence currencies.

Authorities intervene for several reasons: to slow a disorderly or excessively rapid move, to defend a currency floor or ceiling, or to rebuild foreign-exchange reserves. Japan's Ministry of Finance, for example, has a long record of intervening when the yen moves sharply. In 1998 and again in 2022, officials stepped in after rapid yen depreciation. Switzerland's central bank maintained a currency floor against the euro for years before abandoning it abruptly in January 2015 — a reminder that even large reserve holders face limits.

A common misunderstanding is that intervention always works. Economists note that when intervention runs against fundamental forces — large interest-rate differentials, persistent current-account deficits — it often only delays adjustment. Market participants watch official statements and reserve data for clues about intervention activity, since many central banks do not announce operations in real time. Live currency moves are visible on the currencies page, and the what moves exchange rates guide covers intervention alongside other drivers.