Some important weaknesses if the elasticity formula above is related to the measure of elasticities. Elasticities are per se defined as marginal changes. This is also why the basic term often is labelled point elasticity. It is evident from the simple formula that it doesn’t take the functional shape of the relationship between the variables into account. Without full knowledge of the functional form, estimates will not be transferable to other levels of demand without some assumptions such as constant elasticity. When we consider these problems, the point elasticity can be expressed as: