This traces back to Charles Davenant and Gregory King's early formulation on the effect on corn prices of a "defect in the supply of corn." Their little table showed that A defect in the supply of 1/10 (caused) an increase in the price of 3/10 A defect in the supply of 2/10 (caused) an increase in the price of 8/10 A defect in the supply of 3/10 (caused) an increase in the price of 16/10 etc. This table shows up in any number of early sources -- especially Thomas Took's *High and Low Prices* etc. Jim Henderson