Aave changes USDT borrowing rules and loan costs suddenly jump

Aave has lowered the utilization threshold at which borrowing rates for Tether’s USDT rise sharply on its Ethereum Core market, making loans more expensive sooner as pool liquidity tightens.

Using the supply balance in an Oct. 20 recommendation by DeFi risk service provider LlamaRisk, the shift corresponds to roughly 57.8 million USDT more modeled unborrowed liquidity at the threshold.

The change was executed on Oct. 21 in Ethereum block 26,241,799. The threshold fell from 94% utilization, the share of borrowed pool liquidity, to 92%. Borrowers can still go beyond that point, but the rate climbs more sharply once they do.

The trade-off for lenders is earlier pressure on borrowers to preserve withdrawal headroom. The intended cushion remains available to be borrowed or withdrawn.

Aave’s two-slope model increases borrowing rates gradually up to an optimal utilization point, often called the kink, then more sharply between that point and full utilization. Lowering the kink moves the more expensive part of the curve earlier.

The deployed USDT parameters at the Oct. 23 block were a 92% optimal usage ratio, a zero base rate, a 4.5% first slope, and a 10% second slope. Those settings leave the rate at the kink at 4.5% APR and the rate at 100% utilization at 14.5%.

Comparing the curves at the same utilization reveals the cost difference. At a hypothetical 94% utilization, the published prior curve is exactly at its kink and charges 4.5% APR. Under the implemented curve, that same utilization is 2% into the eight-point range above the new kink.

The calculation is 4.5% plus 10% points multiplied by two-eighths, giving 7% APR. That is a conditional comparison at identical utilization, separate from the observed 4.23% borrowing APR on Oct. 23.

For a constant 1 million USDT loan, a 2.5% gap would amount to 25,000 USDT of additional simple annual interest if both modeled rates and the principal stayed unchanged for a full year.

The 92% threshold does not ban borrowing above that level, and the curve’s 14.5% endpoint does not establish that lenders will always have cash available.

LlamaRisk reported 2,892.2 million USDT supplied in its Oct. 20 recommendation. Keeping that supply fixed, a reserve operating at 94% utilization would leave 6% unborrowed, while 92% utilization would leave 8% unborrowed.

Those percentages correspond to 173.53 million and 231.38 million USDT, respectively, for a difference of 57.84 million USDT. It is the difference between two modeled operating points on the same supplied balance.

LlamaRisk separately reported about 417 million USDT already idle in its recommendation, when utilization was below either kink.