Interest Rate Model

When utilization in the market is high, liquidity risk will appear, and as it approaches 100%, liquidity risk will peak. In order to better solve this problem, the interest rate curve of JustLend DAO is divided into two parts with optimal utilization as the dividing line. The slope of the curve is small until optimum utilization is reached, and increases sharply beyond optimum utilization.

The U value can be used to monitor the share of the market’s total assets that have been borrowed at time t . The interest rate Rₜ is defined as below:

if U < Uₒₚₜᵢₘₐₗ : Rₜ = R₀ + Uₜ / Uₒₚₜᵢₘₐₗ * Rₛₗₒₚₑ₁

if U ≥ Uₒₚₜᵢₘₐₗ : Rₜ = R₀ + Rₛₗₒₚₑ₁ + (Uₜ - Uₒₚₜᵢₘₐₗ) / (1 - Uₒₚₜᵢₘₐₗ) * Rₛₗₒₚₑ₂

The interest rate models for all markets are derived from the formula above, with different parameters used for different markets.

  • When U < Uₒₚₜᵢₘₐₗ , the borrowing rate increases slowly with the utilization.

  • When UUₒₚₜᵢₘₐₗ , the borrow interest rates increase sharply with utilization to above 50% APY if the liquidity is fully utilized.

Since the borrowing rate keeps changing with the change of the utilization rate, this characteristic brings certain difficulties to financial planning. Especially for those users who need to stabilize the borrowing interest rate, when calculating the borrowing rate, a certain buffer needs to be added, and at the same time, it is necessary to pay close attention to the capital utilization rate of the market.