市场经济条件下，商品需求量对人们收入变化的敏感性称为收入弹性。数量变化百分比/收入变化百分比为收入弹性。富裕国家的粮食需求收入弹性通常较低，而发展中国家较高。在发展中国家，由于需要，将把收入的很大一部分分配给粮食。食物成为一种强烈的必需品，因此表现出高收入的弹性。在美国这样的富裕国家，食物是必需品，但也被认为是正常的必需品。作为一种正常商品，其收入弹性在0 – +1之间为正，收入增长对食品需求的影响较小。此外，由于有许多不同种类的食品，有不同形式的食品定价、食品计划等，收入可能不会对食品需求产生直接影响。
The sensitivity in response in terms of quantity demanded of a good with respect to the change in income of people in the market economy is called income elasticity. Percentage change in quantity/ percentage change in income is the income elasticity. Income elasticity of demand for food is usually lower in rich countries and higher in developing ones. In developing nations, a high percentage of income will be allotted to foods because of necessity. Foods become a strong necessity and hence exhibit high elasticity with income. In the case of a rich country such as the United States, food is a necessity but is also considered as a normal necessity. As a normal good, it has positive income elasticity between 0 and +1 and income increase has only a smaller percentage impact on demand for food. Moreover, since many different varieties of food are available, with different forms of food pricing, food plans etc, income might not have a direct impact on the demand for food .
Secondly, food is considered as a normal commodity in rich countries and as such is the most basic of their needs. Food security is addressed as being at the bottom of their needs chain and their needs have moved to other higher end ones such as self-actualization as presented in Maslow’s hierarchy of motivation. So income changes rarely have a strong impact on their basic needs.
On the other hand, there are some types of goods that these rich countries would expect to have high income elasticity.
The income elasticity of demand is usually strongly positive for luxury goods. They have an income elasticity of demand which is greater than +1. When there is an increase in income then there is a higher percentage of increase in the demand (Lazonick, 1993). Some of the products that come under luxury goods and that would be considered to be under this elasticity are that of fine wines, spirits, and chocolates, luxury travelling and related services. All these products and services would have high income elasticity in rich countries.