Ey= 1, indicating that the change of income and the change of demand quantity are in the same proportion. Ey= 1

Ey> 1, which shows that the income elasticity is high, that is, the corresponding demand increase is greater than the income increase.

Ey< 1, indicating that the income elasticity is low, that is, the corresponding demand increase is less than the income increase.

Ey=0, which means that no matter how the income changes, the demand quantity remains unchanged.

Ey<0 means to buy less when the income increases and buy more when the income decreases.

In economics, the elasticity of demand for ordinary commodities is positive, income increases, and the demand for ordinary commodities increases. If the income elasticity of demand of a commodity is less than 1, it is a necessity. If the income elasticity of demand of a commodity is greater than 1, it is a luxury or high-grade commodity.

The income elasticity of demand is zero, which means that income will increase and demand will remain unchanged. This commodity is sticky.

The income elasticity of demand is often used as an indicator of healthy economic operation and expected consumption patterns, and it is also a guide for enterprises to make investment decisions. For example, the "elasticity of alternative income" listed below shows that consumers spend a higher proportion of their budgets on cars and restaurants, while spending less on tobacco and butter.