Change in Demand vs. Change in Quantity Demanded


The demand curve represents the demand of a product by the people at a given quantity. The Y-axis gives hypothetical price values for the product, while the x-axis gives hypothetical values for the quantity demand for the product. The demand curve is usually downward sloping and is explained by the law of demand. The coordinates of any given point on the demand curve give a hypothetical quantity demanded, and the price for it (x-value is quantity demanded, y-value is the price of the product). The demand curve is created by the law of demand.

The quantity demanded increases as price for the product decreases, and quantity demand decreases as price increases. This is all explained by the Law of Demand. Price changes and quantity changes usually occur on the demand curve itself, either moving up or down. A change in quantity demanded occurs on the same demand curve, and it either goes up the curve or down. However, a change in demand is a shift of the entire demand curve to either the right or to the left on the graph.deldem.gif So when people say the demand for oil has decreased, its not that the demand for oil has decreased, it is that the quantity of oil demanded has decreased.



As seen in the diagram above, the move from line D1 to D2 is a change in demand. A change in quantity demanded can be seen by a movement along the D1 demand curve.








These above videos explain above and beyond the idea of demand. They directly address the Law of Demand, break it apart and explain it. The videos are highly recommended if you are confused of this idea in any way. The videos are broken up into three parts. They talk about the law of demand, and the demand curve. They explain demand, and show differences between change in demand, and change in quantity demanded. The videos are good educational source.

Question 1- Person A goes to a store and buys 5 boxes of cereal for $3 each. A month later the same person goes to the store and buys only 2 boxes of cereal for $8 each. Assume no other variables have changed. This is a change in...

A) Income
B)Quantity Demanded
C)Demand
D)Supply
E)Stride Gum...Long Lasting...SPIT IT OUT or we will find you!!!!!!!!!!!
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Answer is ??????????????
IT IS B.
= The question tells us that no other variables have changed, so we have to assume that income, and supply are the same. Also we have to assume no determinants of demand changed because the question states that no other variables have changed. From that we know that we have the same demand curve. And the only difference is that price rose, and thus quantity demanded dropped, according to the Law of Demand. It was movement along the same demand curve. Quantity demanded changed from 5 to 2, not the whole demand curve. Thus, the answer is B.

Helpful Websites-
Wikipedia- Demand Curve
Differences between Demand and quantity demanded
Economic Basics