(a) Shift in supply—Shift in supply curve refer to situations of increase or decrease in supply even when own price of the commodity remains constant. Shifts in supply curve are caused by factors, other than own price of the commodity. These are often studied as: 

1. Increase in supply, indicated by forward shift in supply curve. 

2. Decrease in supply, indicated by backward shift in supply curve. 

Three determinants of leftward shift the supply curve are as follows: 

1. Use of outdated technology, causing a fall in efficiency and rise in cost of production. 

2. Decrease in number of firms in the industry. 

3. Increase in taxation.

 (b) Elasticity of Demand: Elasticity of demand means responsiveness of demand due to change in price of the commodity, income of the consumer and price of the related goods. 

Three factors/determinants of elasticity of demand are: 

1. Own price of commodity—Other things being equal, with a rise in own price of the commodity, its demand contracts, and with a fall in price, its demand extends. This inverse relationship between own price of the commodity andits demand, is called law of demand. 

2. Income of the consumer—Change in income of the consumer also influences his demand for different goods, the demand for normal goods tends to increase with increase in income and vice versa. On the other hand, the demand for inferior goods like Coarse grain tends to decrease with increase in income and vice versa. 

3. Expectations—If the consumer expects a significant change in the availability of the concerned commodity in the near future, he may decide to change his present demand for the commodity. If he expects a rise in price in future, he will purchase today and if he expects a fall in price in future he postpones his demand.