Methodology:

Defi Rate Index is a fully transparent index that uses equal weight components of variable DAI (or USDS) and USDC stablecoin lending rates on the two largest DeFi lending protocols, AAVE and Compound.

Defi Rate Index = 0.5 * ( AAVE USDC rate * 0.5 + Compound USDC rate * 0.5 ) + 0.5 * ( AAVE DAI rate: * 0.5 + Compound DAI rate * 0.5 )

Source:

Data is sourced from on-chain data or publicly available APIs once per day at 4 a.m. UTC:
AAVE v3 calculation: link
Compound v3 calculation: link