STBL rewards are paid at a fixed rate APR that changes as a function of the STBL to USDC exchange rate. When the STBL to USDC exchange rate is at 1, the contract pays a max APR of 17.5%. When the exchange rate moves from 1, the APR falls, first quickly (to 11% at 0.99 and 1.01), then more slowly to (to 5% when trading below 0.95 and above 1.05). Attached is a figure highlighting the APR structure.