What Is The Difference Between A Shift Along A Demand Curve And A Shift Of A Demand Curve

What is the difference between a movement along and shift of the demand curve?  Please discuss with reference to DVDs.

 

 

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The basic difference between a move along a demand curve and a change in the curve is that the former is caused by a change in price while the latter is not.  A move along the curve results in a different quantity demanded at a different price.  A change in...

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The basic difference between a move along a demand curve and a change in the curve is that the former is caused by a change in price while the latter is not.  A move along the curve results in a different quantity demanded at a different price.  A change in demand means that a different quantity will be demanded at a given price than was demanded before the change in demand occurred.

Let us look at this with regard to the DVD of a particular movie.  Let us say the price is now $15.  But then the price drops to $10.  All other things being equal, more people will buy the DVD at the lower price.  This is a movement along a given demand curve.  There has been no change in how many people would buy the DVD at $15.  Instead, the price has changed, causing a change in how many people will buy.

Now let us look at how the curve could move.  Let us say the DVD is selling for $15 but then the star of the movie commits a ghastly crime in real life.  His popularity plummets and many fewer people want to buy the movie.  In this case the price can remain at $15 but many fewer people will buy the DVD.  This is an instance in which the demand has actually changed.

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