Until May 2022, algorithmic stablecoins seemed like the future: they promised a stable peg to the dollar without needing to hold reserves in banks. UST (TerraUSD) was the flagship of this approach, with a market cap of $18 billion at its peak. Within a week in May 2022, UST fell from $1 to $0.10 and effectively went to zero. What this meant then and what it means now.
How UST Worked
The peg was maintained not by reserves but by an arbitrage mechanism involving a paired token, Luna. If UST was worth more than $1, you could swap Luna for UST at a profit; if less, the reverse. Under normal conditions, market forces kept the price around the dollar.
The problem lay in one detail: to create UST, you had to burn an equivalent amount of Luna; to redeem UST, new Luna was minted. During a panic-driven mass redemption of UST, Luna issuance grew uncontrollably, Luna's price plummeted, and the arbitrage stopped working. This was a death spiral baked into the design.
What Happened in May 2022
A coordinated attack on UST liquidity in the Curve pool triggered an initial depeg to $0.95. This was a signal for holders: mass redemptions began. Within days, Luna issuance increased thousands of times, and its price collapsed from $80 to $0.0001. The algorithm continued to work as intended — the peg simply could not survive under panic conditions.
Consequences for the Market
The UST/Luna crash triggered the crypto winter of 2022–2023. It dragged down Three Arrows Capital, Celsius, and Voyager into bankruptcy. Regulators gained a ready-made case for banning untested financial instruments.
In Europe, MiCA directly prohibits algorithmic stablecoins without reserves. In the US, similar requirements are being developed.
Do Algorithmic Stablecoins Still Exist?
Yes, but on a smaller scale. FRAX switched to full reserve backing in 2023 (formerly fractional-algorithmic). crvUSD from Curve is an overcollateralized lending stablecoin. GHO from Aave is also overcollateralized. These are not pure algorithmic stablecoins in the spirit of UST — they are collateral-backed stablecoins.
What to Take Away from This Lesson
A stablecoin without reserves is fundamentally unstable under stress. If an issuer promises a peg solely through an algorithm and without backing by real assets, it means the peg will not hold during a panic. Use stablecoins with transparent, audited reserves (USDC, PYUSD), and approach exotic algorithmic solutions with the same caution as high-risk DeFi protocols.
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