Currency Peg

A currency peg is an exchange-rate regime in which a central bank fixes its currency’s value to another currency or basket. The peg can be hard (a rock-solid commitment like the Hong Kong dollar at 7.80 USD) or soft (an announced target that can be adjusted). A peg removes the exchange rate as a tool of monetary policy but provides certainty for trade and investment.

Hard pegs vs. soft pegs

A hard peg is a commitment the central bank will defend at almost any cost. The Hong Kong dollar is pegged at 7.80 USD and has been held there for decades. The Hong Kong Monetary Authority buys and sells at that exact rate, no questions asked. This creates certainty: you know the rate will not move.

A soft peg is an announced target that can be adjusted. The central bank commits to defend it but reserves the right to shift the peg if circumstances change. During the 2008 financial crisis, several emerging-market central banks quietly devalued their soft pegs to ease the burden on their economies.

Hard pegs are more credible but less flexible. Soft pegs are more flexible but less credible.

Why peg to a specific currency?

Most pegs anchor to the US dollar because the dollar is the global reserve currency: it is widely held, widely traded, and has deep, liquid markets. For countries that trade heavily with the US or borrow in dollars, a dollar peg makes sense — it matches their natural exposure.

Some countries peg to the euro (especially in Europe and former colonies in Africa), or to a basket of currencies (to hedge against any single currency strengthening too much).

Bands and crawling pegs

Some pegged currencies maintain a band — they peg to a rate but allow the rate to move within a narrow band. The Czech koruna, for example, was originally allowed to move ±1.5% around its central peg rate. This adds flexibility while keeping the rate stable.

A crawling peg slowly adjusts the peg level over time (e.g., 2% annually), allowing gradual devaluation to offset inflation differentials without a crisis.

The peg constraint

A pegged currency cannot move freely in response to changes in interest rates, inflation, or growth expectations. This leads to the impossible trinity: the country must choose to give up either the peg, free capital flows, or monetary policy autonomy.

In the 1990s, Mexico, Thailand, and other emerging markets learned this lesson painfully. They had pegs they presented as hard (“We will never devalue”), attracted huge capital inflows, and when capital reversed, the pegs broke spectacularly. See currency crisis.

Defending the peg

To maintain a peg, the central bank must hold enough foreign-exchange reserves to buy its own currency if the market is selling. If the peg is at 7.80 and the market is pushing lower, the central bank buys its own currency with dollar reserves. This shrinks its reserves over time.

If reserves run out, the peg breaks. The central bank cannot defend it anymore. This happened to Thailand in 1997, Mexico in 1994, and the UK pound on “Black Wednesday” in 1992 (when Soros’s famous bet broke the pound’s peg to the Deutschmark).

See also