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] ♪