Methodology:

Defi Rate Index is a fully transparent index that uses equal weight components of variable DAI 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 publicly available APIs once per day at 4 a.m. UTC:
AAVE USDC/DAI: link
Compound USDC: link
Compound DAI: link