First outlined by the Italian-born economist Piero Sraffa (1898-1983), own rate of interest was later coined by English economist John Maynard Keynes (1883-1946) in his General Theory. It is defined as the percentage change in a current commodity price compared with its known future price in the market.
Every commodity has its own rate of interest, be it oil, coal or wheat. Each of these can be affected by other commodity interest rates. Thus, future wheat production will be influenced by future oil prices.
P Sraffa, 'Dr Hayek on Money and Capital', Economic Journal, 42 (March, 1932), 42-53;
J M Keynes, The General Theory of Employment, Interest and Money (New York, 1936)