This document discusses methods of measuring price elasticity of demand and provides examples of calculating elasticity using percentage and total expenditure methods. It also lists factors that affect the elasticity of demand, including the availability of substitutes, income level, whether the good is a necessity or luxury, ability to postpone consumption, number of uses, and proportion of income spent on the good. Elasticity is higher for goods with close substitutes, luxuries, those that can be postponed, have multiple uses, or consume a large portion of income, while inelastic for necessities, goods without substitutes, or that consume a small portion of income.