Elasticity concept is very widely used in economics, it refers to an economic function, the dependent variable on the independent variables change the degree of response. To be more specific World steel pipe network editing , the elasticity is 1% of the independent variable changes caused by the dependent variable changes in a few percent. Written formula is: the elasticity is equal to the percentage change in the dependent variable divided by the percentage change caused by this number of changes in the independent variable. Elasticity of demand is an explanation of a demand function, the dependent variable on the independent variables change the degree of response. In the demand function, demand is the dependent variable, factors affecting demand is the independent variable (including product prices, consumer income, prices of related products and advertising, etc World Pipe network informed.). Elasticity of demand refers to demand for the degree of response on the impact of a number of factors change, or that certain factors affecting the demand for change of 1% will cause the demand for change of a few percent.