Why Algorithmic Stablecoins Fail: Death Spirals Explained

Algorithmic stablecoins attempt to peg their value to fiat currencies using code and arbitrage incentives rather than holding dollar reserves. When market panic outpaces system liquidity, these programmed mechanisms fail, triggering hyperinflationary feedback loops. This structural vulnerability routinely leads to complete systemic collapse.

The Mechanics of Algorithmic Pegs

Traditional stablecoins operate similarly to digital money market funds. The issuer accepts a fiat dollar, deposits it in a regulated financial institution, and mints a digital token on a blockchain. If a user wants their fiat back, they redeem the token, and the issuer destroys it while wiring the funds. The peg is maintained because the underlying asset exists independently of the blockchain.

Algorithmic stablecoins remove the fiat reserve. Instead, they rely on a dual-token system governed by smart contracts to balance supply and demand. The system consists of the stablecoin, which is meant to track a fiat currency like the US dollar, and a volatile secondary token, which acts as a shock absorber. The protocol expands and contracts the stablecoin supply to keep its price at exactly $1.

When the stablecoin trades above $1, the protocol incentivizes users to expand the supply, pushing the price down. When it trades below $1, the protocol incentivizes users to contract the supply, pushing the price up. This relies entirely on market participants acting rationally to capture small, risk-free profits.

Endogenous Collateral and Arbitrage Loops

The most common algorithmic model relies on endogenous collateral. This means the collateral backing the stablecoin is created by the same protocol, deriving its value entirely from the market's belief in the protocol's future success.

The stabilization mechanism is an ongoing arbitrage loop. If the stablecoin falls to $0.98, traders can buy it on the open market for 98 cents. The protocol allows them to exchange that one stablecoin for exactly $1.00 worth of the newly minted volatile token. The trader then sells the volatile token for $1.00 on a crypto exchange, pocketing a two-cent profit. This process removes stablecoins from circulation, reducing supply and theoretically restoring the peg to $1.00.

Conversely, if demand pushes the stablecoin to $1.02, a trader can purchase $1.00 worth of the volatile token, burn it via the protocol to mint one stablecoin, and sell that stablecoin for $1.02. This adds stablecoin supply to the market, cooling the price back to the peg.

This system functions smoothly during periods of network growth. As long as there is organic demand for the volatile token, arbitragers can immediately sell their minted tokens to lock in profits. The protocol relies on the assumption that market depth for the volatile token will always exceed the volume of stablecoin redemptions.

Anatomy of a Death Spiral

A death spiral occurs when the fundamental assumption of infinite liquidity breaks down. If panic sets in and a massive number of users decide to exit the stablecoin simultaneously, the protocol must mint an enormous amount of the volatile token to honor the redemptions.

Consider a worked example of a hypothetical algorithmic stablecoin, $ALGOSTABLE, and its volatile counterpart, $VOLATILE. Assume there are 10 million $ALGOSTABLE in circulation. $VOLATILE trades at $10 per token.

If $ALGOSTABLE drops to $0.90, arbitragers buy it and burn it for $1.00 worth of $VOLATILE. For every $ALGOSTABLE burned, the protocol mints 0.1 $VOLATILE. If 1 million $ALGOSTABLE are redeemed quickly, the protocol mints 100,000 new $VOLATILE tokens. The arbitragers immediately dump these 100,000 tokens onto the market to capture their fiat profit.

This sudden surge in selling pressure causes the price of $VOLATILE to drop from $10 to $5. As panic worsens, another 1 million $ALGOSTABLE are redeemed. Because $VOLATILE is now worth only $5, the protocol must mint 0.2 $VOLATILE for every stablecoin burned. This mints 200,000 new tokens, accelerating the supply inflation.

The arbitragers sell these tokens, pushing $VOLATILE down to $1. The next 1 million $ALGOSTABLE redemptions require minting 1 million $VOLATILE tokens. The supply of the volatile token expands exponentially, hyperinflating its supply while driving its price to zero. Arbitragers stop buying the stablecoin because the volatile token lacks the liquidity to be sold for a profit. The peg breaks entirely, and both tokens become worthless.

The TerraUSD (UST) Collapse

The most prominent real-world example of this failure occurred in 2022 with the Terra network, which operated the algorithmic stablecoin $UST and its volatile counterpart, $LUNA. According to a 2022 Federal Reserve working paper on stablecoins, the system grew rapidly due to artificially high yields subsidized by the protocol's treasury.

When large capital outflows triggered a slight depeg of UST, the arbitrage mechanism activated. Users began burning UST to mint LUNA. However, the sheer volume of UST being redeemed overwhelmed the market depth for LUNA. The price of LUNA plummeted, requiring the protocol to mint exponentially more LUNA for every subsequent UST burned.

Within days, the supply of LUNA hyperinflated from hundreds of millions to trillions of tokens. The price of LUNA fell by 99.99%, erasing tens of billions of dollars in market capitalization. With LUNA functionally worthless, the arbitrage mechanism failed entirely, and UST permanently lost its peg. The collapse demonstrated that endogenous collateral cannot survive a concerted bank run.

Fiat and Over-Collateralized Alternatives

To avoid death spirals, modern decentralized finance relies on exogenous collateral—assets that retain value independent of the stablecoin protocol. This is typically achieved through fiat-backing or over-collateralization.

Fiat-backed stablecoins hold cash or Treasury bills in traditional bank accounts. Because the collateral is exogenous, a drop in the stablecoin's market price does not affect the value of the reserves. Users can always redeem the token for the underlying fiat, ensuring the peg is maintained by actual dollar equivalence rather than speculative incentives. For more on how these structures handle stress, see Stablecoin Depegs: Why They Happen and How Pegs Break.

Decentralized alternatives use over-collateralized mechanics. Instead of an unbacked algorithmic expansion, users deposit a volatile but exogenous asset, like ether, into a smart contract to borrow stablecoins. To mint $100 of stablecoins, a user might be required to lock up $150 worth of ether.

If the price of ether drops, the protocol liquidates the collateral on the open market before the collateral value falls below the $100 owed. The stablecoin remains backed by tangible market value at all times, preventing the hyperinflationary feedback loops characteristic of pure algorithmic models.

Common misconceptions

• Algorithmic stablecoins are backed by nothing. They are technically backed by the protocol's volatile companion token. The issue is not a lack of backing, but that the backing is reflexive and loses value at the exact moment it is needed most.
• Smart contracts can prevent a bank run. Code executes exactly as written, but it cannot force external markets to provide liquidity. In a panic, smart contracts will flawlessly execute the hyperinflationary minting that destroys the system.
• All decentralized stablecoins are algorithmic. Decentralized stablecoins can use over-collateralization with exogenous assets. Algorithmic stablecoins are a specific subset that rely on dual-token arbitrage rather than hard collateral.

How this connects to the broader market

The structural fragility of algorithmic stablecoins has heavily influenced global digital asset regulation. Following the collapse of major algorithmic projects, regulatory bodies moved swiftly to differentiate between asset-referenced tokens and algorithmic models.

Under frameworks like the European Union's Markets in Crypto-Assets (MiCA) regulation, algorithmic stablecoins face stringent restrictions or outright bans, as they lack the 1:1 liquid reserve requirements mandated for authorized e-money tokens. Central banks continually point to endogenous collateral models as a source of contagion risk, noting that their failure destroys retail wealth and damages trust in the broader digital asset ecosystem. This regulatory scrutiny is further detailed in ECB and BIS Warn Stablecoins Challenge Monetary Control and Banking Stability.

Market participants now broadly discount uncollateralized stablecoin models, directing capital toward fiat-backed and over-collateralized architectures that provide verifiable, exogenous liquidity.