Interest rates for what? bitcoin? I would expect the cost to borrow a deflationary asset to be very low, if not below zero because the cost to repay said asset will increase in real terms over the course of the loan.
You can see the average cost to borrow BTC on bitfinex
here (data goes back to July 2013), and you can see the last 3 months of the cost to borrow BTC on bitfinex, poloinex and Quoine
here.
You can also use prices on Bitmex futures to calculate effective BTC interest rates, although USD interest rates will also need to be considered. Futures prices more accurately reflect the difference between USD interest rates and BTC interest rates.
The above reflects interest rates for
very well capitalized loans (with automatic liquidation upon the value of collateral falling too low), and is a baseline similar to how the
prime rate is a baseline index for USD based consumer loans.
Consumer loans based on BTC generally have a higher spread over the index than USD based loans given by traditional banks because collecting on loans in the BTC economy is very difficult, loan amounts often too small to economically collect on loans, and most lenders lack the ability to effectively measure risks.
