0:00:00.000,0:00:02.331
♪ [music] ♪

0:00:13.589,0:00:15.190
- [Narrator] Economists[br]use similar terms

0:00:15.190,0:00:17.408
for two things[br]which are quite different:

0:00:17.408,0:00:22.373
a change in the quantity demanded[br]versus a change in demand.

0:00:22.373,0:00:24.710
It can be a little confusing,[br]so let's review.

0:00:25.241,0:00:27.040
A change in quantity demanded

0:00:27.040,0:00:30.754
refers to a movement[br]along a fixed demand curve --

0:00:30.754,0:00:32.975
that's caused by a change in price.

0:00:33.837,0:00:38.271
A change in demand refers[br]to a shift in the demand curve --

0:00:38.271,0:00:40.810
that's caused[br]by one of the shifters:

0:00:40.810,0:00:42.895
income, preferences,

0:00:42.895,0:00:46.237
changes in the price[br]of related goods and so on.

0:00:46.237,0:00:49.005
Let's illustrate the difference[br]with a refreshing example.

0:00:49.005,0:00:50.329
We'll use soda.

0:00:51.284,0:00:53.004
- [Woman 1] Um, don't you mean pop?

0:00:53.004,0:00:54.888
- [Man] That's a coke, y'all!

0:00:54.888,0:00:58.339
- [Woman 2] Actually, soft drink[br]is the most accurate term, so...

0:00:58.339,0:01:01.112
- [Narrator] Fine, we'll just use[br]sugary, fizzy drinks, okay?

0:01:01.112,0:01:04.805
First, let's recall a change[br]in the quantity demanded.

0:01:04.805,0:01:07.454
Suppose the price[br]on sugary, fizzy drinks

0:01:07.454,0:01:09.753
goes from $3 to $4.

0:01:09.753,0:01:11.309
What happens?

0:01:11.309,0:01:16.438
Well, the quantity demanded[br]decreases from 200 to 150.

0:01:16.438,0:01:19.131
There's a decrease[br]in the quantity demanded

0:01:19.131,0:01:22.020
marked by movement[br]along the demand curve.

0:01:22.020,0:01:25.371
But there's no change[br]in the existing demand curve.

0:01:26.138,0:01:28.722
Now, let's look at[br]a change in the demand,

0:01:28.722,0:01:30.947
in this case, a decrease in demand

0:01:30.947,0:01:34.471
of [sighs] sugary, fizzy drinks,

0:01:34.471,0:01:36.939
caused by a viral[br]marketing campaign

0:01:36.939,0:01:40.030
for naturally sweetened[br]sparkling water.

0:01:40.030,0:01:44.137
People just aren't as excited[br]about sugary, fizzy drinks anymore.

0:01:44.137,0:01:47.455
The decrease in demand[br]shifts the entire demand curve

0:01:47.455,0:01:48.836
down and to the left

0:01:48.836,0:01:53.289
and leads, as we know,[br]to a lower quantity at every price.

0:02:01.088,0:02:02.571
In the first case, on the left,

0:02:02.571,0:02:05.155
we have a decrease[br]in the quantity demanded --

0:02:05.155,0:02:08.277
that is a movement[br]along a fixed demand curve.

0:02:08.277,0:02:11.472
In the case on the right,[br]we have a decrease in demand.

0:02:11.472,0:02:15.173
The entire demand curve[br]shifts down and to the left.

0:02:15.173,0:02:16.322
An easy way to remember this

0:02:16.322,0:02:19.906
is that our graph tracks changes[br]in price and quantity.

0:02:19.906,0:02:23.688
If a change occurs in a variable[br]other than price or quantity --

0:02:23.688,0:02:26.706
that is, something[br]not measured on either axis --

0:02:26.706,0:02:29.819
that will represent a shift[br]in the demand curve.

0:02:30.438,0:02:34.607
Prices on the vertical, or y-axis,[br]so a change in price alone,

0:02:34.607,0:02:37.455
will cause movement[br]along the curve.

0:02:37.455,0:02:40.415
A change in income,[br]population, tastes, etc. --

0:02:40.415,0:02:42.672
none of these are measured[br]on either axis,

0:02:42.672,0:02:46.764
and thus, we'll see a shift[br]in the entire demand curve.

0:02:47.322,0:02:48.606
So there you have it.

0:02:48.606,0:02:50.623
Similar terminology[br]can be confusing,

0:02:50.623,0:02:54.005
but if you follow the curves, [br]you won't have to worry.

0:02:57.337,0:02:58.437
If you're a teacher,

0:02:58.437,0:03:00.738
you should check out[br]our Supply and Demand unit plan

0:03:00.738,0:03:02.486
that incorporates this video.

0:03:02.486,0:03:04.950
If you're a learner,[br]make sure this video sticks

0:03:04.950,0:03:07.606
by answering a few[br]quick practice questions.

0:03:07.606,0:03:09.957
Or if you're ready[br]for more microeconomics,

0:03:09.957,0:03:11.623
click for the next video.

0:03:12.605,0:03:15.006
♪ [music] ♪