PED = % change in Quantity Demanded PED = (New QD – Old QD) x100
% change in Price , (New P – Old P) x 100
Inelastic : The PED value is between 0 and -1. It tends to have few substitutes, is necessities, and/or can be
addictive, e.g., alcohol, cigarettes, or petrol.
Elastic : The PED value is between -1 and -∞. It has a lot of substitutes and may be an inferior good.