In this article, I would like to introduce you to the concept of elasticity.
So, What is Elasticity?
Elasticity is a measure of the degree to which one variable would be impacted as a result of change in the other variable.
In MMM, if you have sales as a dependent variable, elasticity would be defined as the degree to which sales would be impacted as a result of change in an input variable.
Or it indicates how responsive sales or market share is towards the various marketing inputs
Usually, elasticity is calculated at 1% or 5%. This could differ based on the analysis level determined by the company
Elasticity at 1% means: How much percent change in sales/ market share is caused by 1 % change in a marketing input.
Now the next question:
How to compute elasticity?
The formula for Elasticity is:

Numerator=Delta(Sales)/Sales
where Delta(Sales) = Sales at time (t + 1)- Sales at time (t)