Determinants of the price elasticity of demand:
1) Is there an available substitute?: Goods with close substitutes have more elastic demand.
2) Is it a luxury or necessity?: Necessities have inelastic demand, luxuries have elastic demand.
3) Weight of the good's cost in the consumers' budget: Goods that represent a relatively small portion of our total budget tend to have inelastic demand.
4) Time period: Price elasticity of demand is higher in the long run because substitute availability increases in the long run.