Reserve Currencies Explained: Why the World Hoards Dollars
A reserve currency is a foreign currency held by central banks and major international institutions as part of their foreign-exchange reserves. Reserve status confers an enormous structural privilege: the issuing country can borrow in its own currency at low cost, run persistent deficits financed by the rest of the world, and have its currency serve as the global medium of exchange for commodities, trade invoicing and financial contracts. Today, the IMF's COFER database shows the US dollar accounting for approximately 58% of disclosed global foreign-exchange reserves as of late 2024 — down from about 71% in 2000, but still dominant by a wide margin.
- The US dollar is the world's primary reserve currency, at ~58% of disclosed global FX reserves (IMF COFER, late 2024).
- Reserve status was anchored at the 1944 Bretton Woods conference and survived the gold-standard collapse in 1971–1973 because of US financial-market depth and legal trust.
- The IMF SDR basket (USD 43.4%, EUR 29.3%, CNY 12.3%, JPY 7.6%, GBP 7.4%) is the closest thing to a multi-currency reserve unit.
- The Triffin dilemma explains why running a reserve currency requires persistent deficits — and why that creates long-run instability.
- Dollar dominance is declining slowly — non-traditional reserve currencies (AUD, CAD, CNY, KRW) are growing — but rapid displacement is unlikely.
Why reserve currencies exist
Central banks hold foreign-exchange reserves for three reasons: to defend their exchange rate if necessary (by buying or selling in FX markets), to pay for essential imports (especially in a crisis), and to signal financial credibility to international investors. To perform all three functions, reserves must be held in currencies that are liquid (easy to buy or sell in large size without moving the market), stable (not prone to sudden devaluation), and backed by trustworthy institutions (rule of law, property rights, deep capital markets).
No currency meets all three requirements as comprehensively as the US dollar — which is why central banks collectively hold roughly $6.7 trillion in dollar assets as of late 2024, versus around $2.4 trillion in euros and about $280 billion in renminbi, according to the IMF.
The history: Bretton Woods to petrodollars
The IMF SDR: a synthetic reserve unit
The Special Drawing Right (SDR) is an international reserve asset created by the IMF in 1969 to supplement member countries' official reserves. The SDR is not a currency; it is a claim on the freely usable currencies of IMF members and can be exchanged for them. Its value is set daily based on a basket of five currencies, reviewed every five years.
The current basket weights, established in the August 2022 SDR review, are:
| Currency | SDR Weight |
|---|---|
| US Dollar (USD) | 43.38% |
| Euro (EUR) | 29.31% |
| Chinese Renminbi (CNY) | 12.28% |
| Japanese Yen (JPY) | 7.59% |
| British Pound Sterling (GBP) | 7.44% |
The SDR basket is a reasonable proxy for the "multi-currency" reserve world that is slowly emerging. Note that the Australian dollar, Canadian dollar, Swiss franc and New Zealand dollar are not in the SDR — which is one reason why this site's macro score covers the eight majors rather than just the SDR five.
The Triffin dilemma: the reserve-currency burden
The economist Robert Triffin identified a fundamental contradiction in the Bretton Woods system in the 1960s. To supply enough dollars for global trade and reserves, the US had to run persistent current-account deficits — exporting more dollars than it received. But those deficits would, over time, undermine confidence that the US could actually redeem dollars for gold at $35 per ounce. The tension resolved when Nixon closed the gold window in 1971.
The modern Triffin dilemma is more subtle but still real. To maintain global dollar liquidity, the US must supply dollars via deficits — which means persistent US trade imbalances are partly a structural consequence of reserve-currency status, not just domestic policy choices. This is a key point in the work of Brad Setser at the Council on Foreign Relations, who documents how central-bank reserve flows distort capital markets and exchange rates.
IMF COFER: tracking the slow de-dollarisation
The IMF Currency Composition of Official Foreign Exchange Reserves (COFER) is the authoritative dataset on how global reserves are allocated. It is published quarterly with a lag and covers approximately 150 reporting economies.
Source: IMF COFER, approximate shares as of Q3 2024. "Other" includes AUD, CAD, CHF, KRW, SGD and other non-traditional reserve currencies.
The key trend: the dollar's share has declined from about 71% in 2000 to about 58% in 2024. The gains have gone not primarily to the euro (which has held roughly steady) but to a diversified basket of non-traditional reserve currencies — including the Australian dollar, Canadian dollar and Korean won. This "diversification into the non-traditional" is a structural, multi-decade trend documented by the IMF.
What reserve status means for exchange rates
Reserve-currency status creates permanent structural demand for the issuing currency that is independent of trade or yield-seeking. Central banks buy dollars not because US Treasuries yield the most, but because they need dollars. This creates several FX dynamics worth understanding:
For the other major currencies, reserve status (or the lack of it) has direct implications:
- EUR — the euro's 20% reserve share gives the European Central Bank a degree of dollar-like structural demand, but the eurozone's lack of a unified bond market limits how far reserve diversification into euros can go. The euro macro score reflects the ECB's rate decisions and eurozone growth.
- JPY — Japan's yen is in the SDR basket but makes up only ~5.5% of global reserves. Safe-haven flows (not reserve accumulation) are the main structural pillar for the yen. See the JPY currency page.
- GBP — Sterling's reserve share (~4.8%) is shrinking slowly. The post-Brexit period weakened the structural case for holding pounds as reserves, though London's financial-market depth keeps the pound relevant.
- AUD, CAD, NZD — these commodity-linked currencies are in the "other" bucket of COFER, slowly growing their reserve share. Their high real yields relative to major safe havens attract reserve managers seeking return on reserves as well as safety.
The future of reserve currencies: slow pluralisation
The most credible academic and institutional consensus — including the IMF's own analysis on dollar dominance — is that the reserve landscape is slowly pluralising rather than experiencing a rapid shift. The renminbi's inclusion in the SDR in 2016 and its slow growth in COFER reserves reflect China's growing economic weight, but capital controls and limited convertibility cap CNY reserve appeal.
What this means for macro traders: the dollar's structural bid from reserve accumulation will persist for years, providing a floor under the US dollar during risk-off episodes and making dollar weakness more gradual than fundamental misvaluation alone would suggest. The how currency strength is calculated post covers how reserve-currency dynamics interact with the macro scoring approach on this platform.
Educational macro context only — not investment advice.