Growth rate of Gross Domestic Product (GDP) is one of the most frequently suggested alternative for Islamic finance transactions. GDP measures value of production in a given year. This alternative avoids reference to interest based benchmarks and reflects pure economic activities in a comprehensive way covering output of all sectors plus prices.
In lease based contracts, such as Ijarah and Diminishing Musharakah, the rental indices can capture the true essence of pricing as per the nature of transaction.
Repo transactions are not compliant with Islamic principles due to the buyback nature of transaction plus the use of interest based securities as underlying assets. However, in commercial contracts where Islamic banks would like to earn return, there is need for a pricing benchmark to mitigate risk as well as ensure transparency in the contract.
Islamic Economics Project 