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