Peg Stability

Peg stability is the degree to which an asset designed to hold a fixed value actually does so. For a stablecoin pegged to the US dollar, it describes how closely the token's market price stays at one dollar on exchanges and in trading between users, how small and brief any deviations are, and whether the peg holds during periods of stress. The term also applies to fixed exchange rate regimes, in which a central bank keeps its currency at a set rate against another currency. Users, exchanges, regulators and businesses that settle payments in stablecoins all watch peg stability closely, because a token that cannot be relied on to hold its value is not useful as money.

Peg stability depends on the design of the asset, the quality of what backs it and the confidence of the market. A loss of the peg is called a depeg, described under stablecoin depeg. The broader idea of fixing one value to another is covered under currency peg.

Different types of stablecoin use different mechanisms:

• Fiat-backed stablecoins. A fiat-backed stablecoin holds cash and short-term government securities as reserves and promises to redeem tokens for one dollar each. If the market price falls below a dollar, approved participants can buy tokens cheaply and redeem them at par, pushing the price back up; if it rises above a dollar, they can create new tokens and sell them. This arbitrage relies on a credible redemption right.
• Crypto-collateralised stablecoins. A crypto-collateralised stablecoin is backed by more crypto collateral than the value of tokens issued, with automatic liquidation of positions if collateral values fall, and interest rate tools to manage supply and demand.
• Algorithmic stablecoins. An algorithmic stablecoin relies mainly on rules that expand or contract supply, often using a second token. These designs have proved the least stable.

Analysts look at several indicators. The simplest is the deviation of the market price from the target, often expressed in basis points, along with how often and for how long the price moves outside a band. Liquidity also matters: a stablecoin traded in deep markets with tight bid-ask spreads can absorb large orders without moving the price, as discussed under stablecoin liquidity. Other signals include redemption volumes, the composition and transparency of reserves, and differences in price between exchanges and blockchains.

Several episodes illustrate the limits of peg stability. In May 2022, TerraUSD, an algorithmic stablecoin, lost its peg and collapsed within days, wiping out tens of billions of dollars in value and prompting regulators worldwide to tighten their approach. In March 2023, USDC, a fiat-backed stablecoin, briefly fell well below a dollar after its issuer disclosed that part of its reserves was held at Silicon Valley Bank, which had failed; the peg recovered once US authorities guaranteed the bank's deposits. These events showed that even well-reserved tokens can depeg if holders doubt that reserves are safe and accessible.

Common features of stable designs include:

• High-quality reserves. Short-dated government securities and cash at several well-capitalised banks, as discussed under stablecoin reserves.
• Transparency. Regular, independent reserve attestations or audits showing reserves at least equal to tokens in circulation.
• Reliable redemption. Clear, timely processes for converting tokens into fiat money at par, described under stablecoin redemption.
• Deep markets. Broad exchange listings and market makers able to trade large volumes near the peg.
• Regulation. Legal frameworks that ring-fence reserves and give holders a claim on them.

Regulators increasingly treat peg stability as a matter of consumer protection and financial stability. The European Union's Markets in Crypto-Assets Regulation (MiCA) requires issuers of e-money tokens to redeem at par at any time and sets rules on reserve assets. In the United States, federal stablecoin legislation enacted in 2025 requires payment stablecoins to be backed one for one by high-quality liquid assets and sets disclosure requirements. Rules in Singapore, Hong Kong and other jurisdictions follow similar principles. Supervisors expect issuers to stress-test their reserves and liquidity against large, sudden redemptions.

Even well-designed stablecoins face risks to their peg: bank failures affecting reserve deposits, sharp falls in the value of reserve securities, operational problems that halt redemptions, legal actions that freeze funds, and runs driven by rumours on social media. For crypto-collateralised tokens, a rapid fall in collateral prices can overwhelm liquidation mechanisms. Users can manage these risks by understanding how a token maintains its peg and by diversifying across issuers.