0:00:00.393,0:00:03.211 ♪ [music] ♪ 0:00:13.809,0:00:15.610 - [Narrator] Economists[br]use similar terms 0:00:15.610,0:00:17.628 for two things[br]which are quite different: 0:00:17.628,0:00:23.011 a change in the quantity demanded[br]versus a change in demand. 0:00:23.011,0:00:25.461 It can be a little confusing,[br]so let's review. 0:00:25.461,0:00:27.260 A change in quantity demanded 0:00:27.260,0:00:30.974 refers to a movement[br]along a fixed demand curve -- 0:00:30.974,0:00:32.973 that's caused by a change in price. 0:00:34.057,0:00:38.491 Change in demand refers to[br]a shift in the demand curve -- 0:00:38.491,0:00:41.207 that's caused by one[br]of the shifter's income, 0:00:41.207,0:00:46.457 preferences, changes[br]in the price of goods and so on. 0:00:46.457,0:00:49.225 Let's illustrate the difference[br]with a refreshing example. 0:00:49.225,0:00:51.875 We'll use soda. 0:00:51.875,0:00:53.224 Um, don't you mean pop? 0:00:53.224,0:00:55.108 That's coke, y'all! 0:00:55.108,0:00:58.559 Actually, soft drink[br]is the most accurate term, so... 0:00:58.559,0:01:01.332 - [Narrator] Fine, we'll just use[br]sugary, fizzy drink, okay? 0:01:01.332,0:01:05.025 First, let's recall a change[br]in the quantity demanded. 0:01:05.025,0:01:07.674 Suppose the price[br]on sugary, fizzy drinks 0:01:07.674,0:01:09.973 goes from \$3 to \$4. 0:01:09.973,0:01:11.459 What happens? 0:01:11.459,0:01:16.658 Well, the quantity demanded[br]decreases from 200 to 250. 0:01:16.658,0:01:19.225 There's a decrease[br]in the quantity demanded 0:01:19.225,0:01:22.240 marked by movement[br]along the demand curve. 0:01:22.240,0:01:25.291 But there's no change[br]in the existing demand curve. 0:01:26.358,0:01:28.942 Now, let's look at[br]a change in demand, 0:01:28.942,0:01:31.658 in this case, decrease[br]in the demand of 0:01:32.593,0:01:34.691 (sighs) sugary, fizzy drinks 0:01:34.691,0:01:37.159 caused by a viral[br]marketing campaign 0:01:37.159,0:01:40.142 for naturally sweetened,[br]sparkling water. 0:01:40.142,0:01:44.259 People just aren't as excited[br]about sugary, fizzy drink anymore. 0:01:44.259,0:01:47.675 The decrease in demand[br]shifts the entire demand curve 0:01:47.675,0:01:49.056 down into the left 0:01:49.056,0:01:53.509 and leaves, as we know,[br]to a lower quantity at every price. 0:02:01.308,0:02:02.791 In the first case, on the left, 0:02:02.791,0:02:05.375 we have a decrease[br]in the quantity demanded -- 0:02:05.375,0:02:08.676 that is a movement[br]along a fixed demand curve. 0:02:08.676,0:02:10.041 In the case on the right,[br]we have a decrease in demand, 0:02:10.041,0:02:15.393 the entire demand curve[br]shifts down into the left. 0:02:15.393,0:02:16.542 An easy way to remember this 0:02:16.542,0:02:20.126 is that our graph track changes[br]in price and quantity. 0:02:20.126,0:02:23.908 If a change occurs in a variable[br]other than price or quantity -- 0:02:23.908,0:02:26.926 that is, something[br]not measured on either axis -- 0:02:26.926,0:02:30.658 that will represent a shift[br]in the demand curve. 0:02:30.658,0:02:34.827 Prices on the vertical or y-axis,[br]so change in price alone, 0:02:34.827,0:02:37.675 will cause movement[br]along the curve. 0:02:37.675,0:02:40.526 A change in income,[br]population, tastes, etc. -- 0:02:40.526,0:02:42.892 none of these are measured[br]on either axis 0:02:42.892,0:02:47.542 and thus, we'll see a shift[br]in the entire demand curve. 0:02:47.542,0:02:48.826 So there you have it. 0:02:48.826,0:02:50.676 Similar terminology[br]can be confusing, 0:02:50.676,0:02:54.225 but if you follow the curves, [br]you won't have to worry. 0:02:57.557,0:02:58.657 If you're a teacher, 0:02:58.657,0:03:00.958 you should check out[br]our supply in demand [ ] 0:03:00.958,0:03:02.706 that incorporates this video. 0:03:02.706,0:03:05.074 If you're a learner,[br]make sure this video sticks 0:03:05.074,0:03:07.826 by answering a few[br]quick practice questions. 0:03:07.826,0:03:10.108 Or if you're ready[br]for more microeconomics, 0:03:10.108,0:03:11.843 click for the next video. 0:03:12.825,0:03:15.226 ♪ [music] ♪