AP MicroeconomicsElasticity
Midpoint Method
The midpoint method calculates elasticity using the average of the two prices and quantities, so it gives the same value in either direction.
It fixes the problem that ordinary percentage changes differ depending on the starting point. The change is divided by the midpoint (average) of the start and end values. The College Board uses it for AP elasticity calculations.
Formula / Example
Elasticity = [(Q₂−Q₁)/((Q₁+Q₂)/2)] ÷ [(P₂−P₁)/((P₁+P₂)/2)].
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