Collateral

How collateral works

The mechanic is symmetric for borrower and lender. The borrower pledges an asset to back the loan; the lender retains a legal claim on the asset until the loan is repaid. If the borrower defaults, the lender exercises that claim — repossesses or forecloses on the asset, sells it, and applies the proceeds to the loan balance. Any shortfall is still owed by the borrower; any surplus is returned.

Common examples in everyday finance:

• Mortgage — the home is collateral. Default leads to foreclosure.
• Auto loan — the vehicle is collateral. Default leads to repossession.
• Margin loan — the securities in the brokerage account are collateral.
• Pawnshop loan — the pledged item is held physically.
• Asset-based business loan — accounts receivable or inventory pledged.

Why secured loans are cheaper

Collateral reduces the lender's risk: even if the borrower defaults, the lender can recover from the underlying asset. That risk reduction shows up as a lower interest rate. A 30-year mortgage at 7% might be paired with a 23% credit card from the same person — the difference is mostly the existence of collateral.

Unsecured personal loans usually fall in between, with rates depending on credit score, income, and other factors.

Loan-to-value (LTV)

The relationship between the loan size and the value of the collateral is the loan-to-value ratio:

LTV = Loan Amount / Collateral Value

Lenders typically cap LTV based on volatility and recoverability. Mortgages commonly allow 80% LTV (more with insurance); auto loans up to 100% or higher (but the car depreciates fast, creating "underwater" positions). Margin loans on stocks vary by stock; the most volatile stocks have stricter limits.

In DeFi lending, LTV varies by asset and is enforced strictly by smart contract. ETH might allow 75% LTV; volatile altcoins much less. If the position crosses a "liquidation threshold" (slightly higher than the LTV), automatic liquidators repay part of the debt and seize collateral plus a penalty.

Liquidation mechanics

When collateral falls below required thresholds:

• Traditional finance — the lender issues a margin call (for securities) or initiates legal foreclosure proceedings. Process can take days to months.
• DeFi — automated liquidator bots execute on-chain, typically within minutes of crossing the threshold. No grace period; no manual review.

The DeFi liquidation speed has both benefits (creditors are protected automatically; bad debt is rare) and risks (cascading liquidations during sharp price moves can wipe out positions that might have recovered).

Cross-collateralization

Some lending arrangements pool multiple assets as collective collateral for one loan or set of loans. Cross-collateralization protects lenders by diversifying recovery sources but exposes borrowers — a default on any single loan can put all the pooled assets at risk.

The 2022 bear market exposed how cross-collateralization can backfire. Several CeFi lenders had cross-collateralized institutional borrowers (3AC, Alameda) whose entire collateral base imploded simultaneously, producing larger losses than the lenders' standalone risk models predicted.

Why collateral matters for the financial system

Most credit creation in modern economies is collateralized in some form. Banks pledge securities to access central-bank liquidity; corporations pledge receivables for working-capital lines; households pledge homes for mortgages. The recursive structure means that asset-price collapses don't just affect asset holders — they undermine the collateral chain that supports the broader credit system. The 2008 financial crisis was fundamentally a collateral crisis: when mortgage values fell, the chain of derivatives and loans built on top of them unwound.