How Stablecoin Pegs Actually Work: The Market Maker Dynamics Behind Dollar Stability

Stablecoins hold more than $300 billion in combined market capitalization, yet the mechanics that keep each token at $1.00 are poorly understood even by experienced crypto users. The standard explanation is "backed by reserves." That is necessary but not sufficient. Reserves sitting in a bank account do not, by themselves, make a secondary-market token trade at par. What actually keeps USDT at $1.0001 and USDC at $0.9999 is a layered system of authorized participants, primary-market arbitrage, CEX order books, DEX liquidity pools, and market makers operating across all of them simultaneously.

This article breaks down that machinery: who participates, how the arbitrage loops work, why the peg never lands on exactly $1.00, and what happens when the system is stress-tested.

Primary Market vs. Secondary Market

Every major fiat-backed stablecoin operates across two distinct markets. Understanding the boundary between them is the single most important concept in peg mechanics.

The Primary Market: Creation and Redemption

The primary market is the direct relationship between the stablecoin issuer and its authorized participants. This channel functions almost identically to how ETF shares are created and redeemed through authorized participants in traditional finance. An authorized participant wires US dollars to the issuer, the issuer mints stablecoins at par (1 token per $1), and delivers them on-chain. In reverse, the participant sends tokens to the issuer, which burns them and wires dollars back.

Access to this channel is gated. Tether requires a minimum transaction of $100,000 and charges the greater of $1,000 or 0.1% as a redemption fee. Circle's Circle Mint program provides free minting for qualified institutions, but as of March 2026, redemptions above $40 million per day incur tiered fees of 2 to 5 basis points. Both issuers require full KYC/AML onboarding before granting access.

Why gating matters: Primary-market access is restricted to institutional counterparties: OTC desks, exchanges, and large market makers. Retail users never mint or redeem directly with Tether or Circle. This restriction creates a natural spread between the primary and secondary markets, which is exactly the profit opportunity that incentivizes market makers to keep the peg tight.

The Secondary Market: Where Everyone Else Trades

The secondary market is everywhere stablecoins actually change hands: centralized exchanges, decentralized exchanges, OTC desks, and peer-to-peer transfers. Prices here are set by supply and demand, not by the issuer. When you see USDT quoted at $1.0002 on Binance, that is a secondary-market price, not a reflection of Tether's redemption rate.

The peg holds because authorized participants arbitrage the gap between these two markets. If secondary-market price drops below $1.00, they buy cheap tokens and redeem at par, pocketing the spread. If the price rises above $1.00, they mint new tokens at par and sell them on the open market. This creation/redemption loop is the gravitational anchor of the entire system.

The Arbitrage Loop: How Stablecoins Return to $1.00

The stablecoin arbitrage loop is the core peg-restoration mechanism. It operates in two directions depending on whether the token trades above or below par.

When the Price Falls Below $1.00

1. USDC trades at $0.997 on secondary markets due to selling pressure
2. An authorized participant (e.g., Cumberland, Wintermute) buys USDC at $0.997
3. They submit a redemption request to Circle via Circle Mint
4. Circle burns the tokens and wires $1.00 per token to the participant
5. The participant profits $0.003 per token (minus fees and capital cost)
6. The buying pressure from step 2 pushes the secondary price back toward $1.00

When the Price Rises Above $1.00

1. USDT trades at $1.003 on secondary markets due to demand surge
2. An authorized participant wires $1.00 per token to Tether
3. Tether mints new USDT and delivers them to the participant
4. The participant sells the freshly minted USDT at $1.003
5. The participant profits $0.003 per token (minus fees)
6. The new supply from step 4 pushes the secondary price back toward $1.00

Why the peg is never exactly $1.00: Minting and redemption involve real costs: wire transfer fees, time delay (redemptions can take 1 to 3 business days), KYC overhead, and issuer fees. These costs create a band, typically $0.997 to $1.003, within which arbitrage is not profitable enough to execute. The price oscillates within this band rather than snapping precisely to $1.00.

Who Are the Market Makers?

The firms that maintain stablecoin pegs are a small group of institutional market makers and OTC desks with direct issuer relationships. Their operations span centralized exchanges, decentralized venues, and the primary creation/redemption channel simultaneously.

These firms profit from the bid-ask spread on every completed round-trip trade, and from the creation/redemption arbitrage when prices drift outside the no-arbitrage band. Their continuous quoting activity is what makes stablecoin order books deep enough for the peg to hold against large trades.

CEX Order Books: The Visible Peg

Centralized exchanges are where most stablecoin volume settles. On Binance, the USDCUSDT pair processes roughly $2.8 billion in daily volume as of mid-2026, making it the most liquid stablecoin pair in the market. The USDT/USD pair on Coinbase, Kraken, and other fiat-denominated exchanges provides the direct dollar price signal.

Market makers maintain tight order book depth around $1.00. On major venues, the bid-ask spread for USDT/USD and USDC/USD pairs is typically under 1 basis point during normal conditions. This means a trader can buy or sell millions of dollars of stablecoins without pushing the price more than a fraction of a cent from par.

The Order Book as Shock Absorber

When large sell orders arrive, resting bids placed by market makers absorb the impact. A market maker quoting a $5 million bid at $0.9999 and a $5 million ask at $1.0001 earns $100 on every full round-trip, but more importantly, that liquidity prevents a single trade from moving the price significantly. The depth of the order book, not the existence of reserves, is what prevents intra-day volatility.

DEX Liquidity: Curve, Uniswap, and On-Chain Peg Stability

On-chain, two DEX architectures play distinct roles in peg maintenance: Curve Finance's StableSwap invariant and Uniswap's concentrated liquidity positions.

Curve's StableSwap and the 3pool

Curve Finance pioneered an AMM design specifically optimized for same-peg assets. The StableSwap invariant is a hybrid between a constant-sum formula (which would allow 1:1 swaps but could be drained) and a constant-product formula (which provides infinite liquidity but with high slippage). The amplification coefficient (A) controls how tightly the pool clings to the peg. For the USDC/DAI/USDT 3pool, A is set to 10,000, concentrating nearly all liquidity within a narrow band around $1.00.

The result: multi-million dollar swaps between major stablecoins with slippage under 1 basis point. When the pool is balanced at roughly 33% each, swaps behave almost like 1:1 exchanges. As imbalances grow, the invariant automatically increases the price of the scarce asset and decreases the price of the surplus asset, creating incentives for arbitrageurs to rebalance.

Uniswap Concentrated Liquidity

Uniswap v3 and v4 allow liquidity providers to concentrate capital within specific price ranges. For stablecoin pairs, LPs can deploy 99% of their capital within the $0.995 to $1.005 range, dramatically increasing capital efficiency. The USDC/USDT 0.01% fee tier pool on Ethereum processes tens of millions in daily volume with liquidity concentrated tightly at the peg.

This concentrated approach means that on-chain pool depth at the peg can exceed comparable Curve pools while deploying significantly less total capital. The tradeoff is that LPs take on more active management responsibility, adjusting ranges as conditions shift.

Stress Test: The March 2023 USDC Depeg

The most instructive depeg event in fiat-backed stablecoin history occurred on March 10 to 13, 2023, when USDC broke its peg following the collapse of Silicon Valley Bank. The mechanics of the depeg and recovery reveal exactly how the system described above behaves under extreme stress.

The Trigger

On March 10, Circle disclosed that approximately $3.3 billion of USDC's roughly $40 billion in reserves (about 8%) were held at Silicon Valley Bank, which had been shut down by California regulators that morning. The question was immediate: could Circle redeem at par if 8% of the backing was frozen?

The Arbitrage Loop Breaks

Under normal conditions, arbitrageurs would buy USDC at a discount and redeem at par, profiting from the spread while restoring the peg. But the SVB revelation introduced counterparty risk into the redemption leg. If Circle could not access $3.3 billion of its reserves, the guaranteed $1.00 redemption was in question. Without a reliable redemption floor, the arbitrage loop that normally keeps the peg collapsed.

USDC fell as low as $0.87 on some exchanges. The critical failure was not the reserves themselves but the uncertainty about whether the redemption channel would function.

Curve 3pool: The On-Chain Panic Meter

The Curve 3pool served as a real-time gauge of market sentiment. Under normal conditions, the pool holds roughly equal proportions of USDC, USDT, and DAI. Within hours of the disclosure, the pool composition shifted dramatically as traders dumped USDC: the USDC share surged from 33% to over 83%, while USDT collapsed to just 1.5% of the pool. Curve processed $6.03 billion in volume on March 11 alone, its highest ever single-day figure.

Contagion Through Collateral

The depeg propagated to DAI and FRAX, both of which used USDC as significant collateral. Since USDC represented over half of DAI's backing at the time, DAI dropped to the $0.96 to $0.97 range. This demonstrates how DeFi composability can transmit stress: a single issuer's banking relationship cascaded through collateral chains across the entire stablecoin ecosystem.

The Recovery

On Sunday, March 12, the FDIC announced a systemic risk exception, guaranteeing all SVB depositors would be made whole, including Circle's $3.3 billion. With the redemption floor restored, the arbitrage loop reactivated immediately. Market makers bought discounted USDC knowing Circle could honor 1:1 redemptions. USDC returned to $1.00 within approximately three days.

The lesson: the peg broke not because reserves were insufficient (Circle still had 92% of backing available) but because the arbitrage mechanism requires certainty about the redemption channel. Remove that certainty, even temporarily, and the peg unravels.

Fiat-Backed vs. Algorithmic: Why the Peg Mechanisms Are Fundamentally Different

The mechanics described above apply to fiat-backed stablecoins like USDT, USDC, and USDB. Algorithmic stablecoins use an entirely different approach, and the distinction matters for understanding peg reliability.

Fiat-Backed: Exogenous Collateral

Fiat-backed stablecoins anchor their peg to external, dollar-denominated assets: cash, Treasury bills, money market funds. The reserve exists independently of the stablecoin's market dynamics. When selling pressure hits, the redemption channel converts tokens into real dollars held outside the crypto system. This exogenous backing means the arbitrage loop has a hard floor: as long as the issuer is solvent and operationally functional, 1 token can always become $1.00.

Algorithmic: Endogenous Collateral

Algorithmic stablecoins like the now-defunct UST used a mint-and-burn mechanism with a companion token (LUNA). When UST dropped below $1.00, arbitrageurs could burn 1 UST and receive $1.00 worth of LUNA. This worked as long as LUNA maintained its market value. But when selling pressure on UST caused mass minting of LUNA, LUNA's price collapsed, making each redemption worth less, which increased selling pressure on UST: a death spiral. In May 2022, this feedback loop destroyed roughly $40 billion in value within a week.

The key difference is reflexivity. Fiat-backed peg mechanics are self-correcting: price deviations create profitable arbitrage opportunities that pull the price back. Algorithmic mechanics can be self-reinforcing: price deviations can trigger dynamics that push the price further away. No pure algorithmic stablecoin design has recovered from a major depeg event.

The Creation/Redemption Flow: Step by Step

The following describes the complete lifecycle of a stablecoin arbitrage trade through the primary market. This is the core mechanism that every other layer of peg stability depends on.

Redemption Flow (Price Below Par)

1. Market maker observes USDC trading at $0.996 on Binance
2. Market maker buys 10 million USDC on Binance for $9,960,000
3. Market maker submits redemption request via Circle Mint API
4. Circle verifies the request, burns 10 million USDC on-chain
5. Circle initiates wire transfer of $10,000,000 to market maker's bank account (1 to 3 business day settlement)
6. Gross profit: $40,000 minus wire fees, Circle redemption fees, and cost of capital for the settlement period

Creation Flow (Price Above Par)

1. Market maker observes USDT trading at $1.004 on secondary markets
2. Market maker wires $10,000,000 to Tether's banking partner
3. Tether verifies receipt and mints 10 million USDT on the requested blockchain
4. Market maker sells 10 million USDT on exchanges at $1.004
5. Gross profit: $40,000 minus Tether's minting fee and transfer costs

The latency in this loop matters. Wire transfers are not instant. During the hours or days between purchasing discounted tokens and receiving fiat from redemption, the market maker bears price risk: the secondary-market price might recover before they complete the trade, or it might fall further. This capital-at-risk cost is why the no-arbitrage band exists and why stablecoins persistently trade at small deviations from par.

Why USDT Often Trades at a Premium

USDT frequently trades at a small premium to $1.00, typically around $1.0001 to $1.0003 on major exchanges. Several structural factors explain this persistent skew.

• Tether's $100,000 minimum redemption and 0.1% fee create a wider no-arbitrage band than Circle's more institutional-friendly terms
• USDT is the dominant quote currency in crypto trading, creating constant demand from traders who need it to enter positions
• In emerging markets where direct dollar access is limited, USDT often carries a premium as a dollar-equivalent store of value
• Tether's minting process can take longer than Circle's, creating a lag between demand and supply expansion

USDC tends to trade closer to par because Circle Mint's API-integrated minting and redemption allows faster arbitrage execution, and its primary users (institutional market makers in US-regulated markets) have lower friction accessing the primary channel.

The Role of Liquidity Depth

The depth of liquidity, not just the existence of reserves, determines how well a stablecoin absorbs shocks. A stablecoin with $10 billion in reserves but $1 million in order book depth would depeg on any reasonably large sell order. Reserves provide the floor; liquidity provides the stability between floor and ceiling.

Where Liquidity Concentrates

Stablecoin liquidity is distributed across venues in a roughly predictable pattern. The deepest liquidity for USDT and USDC sits on Binance, with additional depth on Coinbase, Kraken, and OKX. On-chain, Curve's 3pool and Uniswap's concentrated liquidity positions provide the deepest DEX pools. The total stablecoin-to-stablecoin DEX volume across Curve and Uniswap runs into billions of dollars weekly.

For newer or smaller stablecoins, Curve's metapool architecture offers a bootstrapping mechanism: a new stablecoin can pair against the 3pool, instantly accessing USDC/USDT/DAI liquidity without needing to build its own pool depth from scratch. This is one of the most important infrastructure primitives in stablecoin market design.

Implications for Stablecoin Payment Systems

The mechanics described in this article have direct consequences for any system that settles payments in stablecoins. Payment processors, wallets, and settlement layers all depend on the peg holding within tight tolerances during the settlement window.

For payment applications, the key consideration is which layer of peg stability they depend on. Settling on a CEX with deep order books provides the tightest spreads. Settling on-chain through DEX pools may introduce slightly wider spreads but offers permissionless, 24/7 access. The choice depends on the use case, regulatory requirements, and user base.

Spark settles payments in USDB, a dollar-pegged stablecoin issued by Brale, a regulated stablecoin-as-a-service provider registered as an MSB with FinCEN and licensed in 44 US states. USDB is fully backed 1:1 by US Treasury bills and cash equivalents held in segregated, bankruptcy-remote accounts, with monthly reserve attestations by an independent CPA. This structure ensures the redemption channel that anchors the peg is backed by regulated infrastructure and transparent reserves. For wallets building on Spark, like General Bread, understanding these peg dynamics helps contextualize the stability guarantees their users depend on.

For a deeper comparison of how different stablecoins handle peg maintenance, see our stablecoin peg mechanisms comparison. Developers building on Spark can explore the Spark SDK documentation for integration details on stablecoin settlement.

Key Takeaways

• Stablecoin pegs are maintained by arbitrage loops between primary markets (creation/redemption at the issuer) and secondary markets (exchanges and DEXs), not simply by the existence of reserves
• A small group of institutional market makers with direct issuer access execute the arbitrage that restores the peg when it drifts
• The peg never sits precisely at $1.00 because minting and redemption carry real costs (fees, settlement latency, capital risk) that create a no-arbitrage band
• DEX liquidity on Curve and Uniswap provides an on-chain peg-stability layer that supplements CEX order books
• Fiat-backed pegs are self-correcting under stress: price deviations create arbitrage incentives. Algorithmic pegs can be self-reinforcing: price deviations can trigger spirals
• The March 2023 USDC depeg demonstrated that peg stability depends entirely on the market's confidence in the redemption channel, not on the total reserve size

This article is for educational purposes only. It does not constitute financial or investment advice. Bitcoin and Layer 2 protocols involve technical and financial risk. Always do your own research and understand the tradeoffs before using any protocol.