Question

what is different between a changed in demanded and a change in quantity demanded?

Answer 1

Change in demand is due to the change in other factors (i.e change in income, chnage in prices of substitue or complimentary goods, change in tastes and preferences etc.) while price is constant. It is also known as increase or decrease of demand. The change is represented by the shift in the demand curve.

When the demand increases at a given price, due to other factors, it is known as increase in demand. It is represented by rightward shift of the demand curve.

When the demand decreases at a given price, due to other factors, it is known as decrease in demand. It is represented by leftward shift of the demand curve.

For example: Coffee and tea are substitue goods. When the prices of coffee decreases, the demand of the tea will decrease at a given price because now the consumers will buy more of coffee and less of tea.

Change in quantity demanded is due to the change in price while other factors are constant. It is also known as expansion or contraction of demand. This change is represented by the movement along the demand curve.

When the quantity demanded increases with the decrease in price it is known as expansion of demand. It is represented by the downward movement along the demand curve.

When the quantity demanded decreases with the increase in price it is known as contraction of demand. It is represented by the upward movement along the demand curve.

For example : With the increase / decrease in the price of milk the quantity demanded will decrease / increase.