PED

• Elastic

  when PED is greater than 1. Change in demand is proportionately greater than change in price
• Perfectly elastic 


  PED = infinity
• Inelastic

  when PED is less than 1. Change in demand is proportionately less than change in price
• Perfectly inelastic

  PED = 0
• Formula

  % change in Qd/% change in price
• Total expenditure

  Quantity bought multiplied by average price of product
• Unitary elasticity

  PED = 1