YED + XED

• Complements

  Goods that are purchased with another good to satisfy a want. Have negative XED.
• YED Formula

  % change in Qd/% change in Y
• XED Formula

  % change in Qd of x/% change in price of y
• Inferior goods

  Demand falls when income increases, have negative YED
• Normal goods

  Demand increases when income increases, positive YED
• Substitutes

  goods that can be replaced by another good and still provide similar benefits. have positive XED