A currency peg breaks when markets conclude the central bank will run out of the reserves or the will needed to defend it, and everything else in peg economics is commentary on that single sentence. The mechanics are simple: a central bank promises to exchange its currency for dollars — or a basket — at a fixed rate, standing ready to buy its own currency with reserves when it weakens and print-and-sell when it strengthens. Switzerland's floor against the euro, abandoned in January 2015 after nearly 200 billion francs of accumulation, the British pound's 1992 ejection from the European exchange-rate mechanism, Argentina's serial collapses including the 2023-2024 peso devaluation before its new regime: every episode is the same arc — defense, doubt, capitulation — differing only in the size of the bill.
Why do states peg at all?
For the same reasons anyone fixes a price: credibility and trade. A peg imports the anchor country's monetary discipline, which matters most for economies whose own inflation record has destroyed domestic trust — Hong Kong's currency board against the dollar since 1983, the Gulf states' dollar pegs that underpin their hydrocarbon pricing, and the Baltic states' hard-peg ladders that ended in euro adoption. Exporters and importers gain a stable planning horizon; small open economies gain a nominal anchor they could not otherwise build. The economic literature is broadly supportive of pegs that are backed by institutions and broadly contemptuous of pegs that substitute for them: the arrangement amplifies whatever discipline already exists, including its absence.
What does defending a peg actually cost?
Three currencies of payment. Reserves: defending against devaluation pressure means selling foreign assets, and reserve levels are published weekly in most systems — a visibly falling line is a countdown clock markets can read, which is why central banks ration the information and why analysts at the IMF track reserve adequacy so closely. Interest rates: the peg's interest rate is set in the anchor country, so defending an overvalued rate means higher domestic rates than the economy can comfortably bear — the tool that broke Britain in 1992, when double-digit rates could not outlast speculators who could borrow against a one-way bet. And credibility itself: each unsuccessful intervention teaches markets the ceiling of official willingness, a lesson they price immediately.
What are the classic warning signs?
A recurring quartet. Reserves falling while the peg holds officially. A parallel or black-market rate diverging from the official one — the gap between Venezuela's official and market rates became a real-time index of the regime's fiction. Domestic rates forced upward beyond business-cycle logic. And import compression: when defending the currency means rationing dollars, goods disappear before prices do, and queues become the visible exchange rate. Argentina's 2023 pre-devaluation crawl — official rates moving in steps while parallel rates ran far ahead — displayed the entire pattern before the December 2023 devaluation of more than 50 per cent under the new Milei government's stabilization program, later accompanied by a revised crawling peg and, by 2025, discussions of a full currency-board-style regime.
Can a peg be credible forever?
Currency boards — where every unit of domestic base money is fully backed by foreign reserves and convertibility is statutory — come closest: Hong Kong's arrangement has survived the 1997 Asian crisis, 2008 and every attack since, at the price of importing US monetary policy wholesale. Dollarization or euroization removes the question by removing the currency, as Ecuador did in 2000 and Zimbabwe attempted repeatedly in chaotic form. But the general pattern holds: pegs are policy commitments, not laws of nature, and they fail when the political coalition behind them changes. The 2015 Swiss abandonment was executed overnight, without crisis, because the central bank judged the accumulating cost higher than the credibility loss — proof that even successful pegs are held at the pleasure of their defenders.
What should a reader watch when a peg is in the news?
Four numbers: the published reserve level and its trajectory; the gap between official and parallel rates; the interest-rate differential against the anchor; and the trade balance that ultimately determines whether the peg is defending fundamentals or fighting them. Pegs that survive quietly defend fundamentals. Pegs that make headlines are usually fighting them, and the market — being a price for the future of a promise — usually gets the verdict before the central bank admits it.
For more context, read How Does the IMF Decide What a Country Can Borrow?.
For more context, read central bank gold audit.
For more context, read Sovereign Default Has a Playbook Now. It Barely Works.