1, the demand is completely inelastic, that is, E= 0. In this case, the demand will not change no matter how the price changes. For example, the demand for insulin by diabetics is like this.

2. The demand is completely elastic, that is, E =∞. In this case, when the price is fixed, the demand is infinite. For example, banks buy gold at a fixed price, no matter how much gold there is, they can buy it at this price, and the demand for gold by banks is unlimited.

3. The demand elasticity is single, that is, E = 1. In this case, the ratio of demand change is equal to the ratio of price change. The above three situations are special cases of demand elasticity, which are rare in real life. There are two common types in reality.

4, demand inelastic, that is, 0

5. Flexible demand, namely 1