0:00:00.302,0:00:02.627 So, we've been going through all of the others things 0:00:02.627,0:00:04.953 that we were assuming are held constant 0:00:04.953,0:00:08.370 in order to be moving along one demand curve. 0:00:08.370,0:00:10.033 And now let's list a few other[s]. 0:00:10.033,0:00:11.511 And before I do any more of them, 0:00:11.511,0:00:12.996 let's talk about the ones we already talked about. 0:00:12.996,0:00:16.322 So – one– we said that one of the things we held constant – 0:00:16.322,0:00:17.452 (Let me write this down.) 0:00:17.452,0:00:22.258 So – (WRITING: held constant.) 0:00:22.258,0:00:25.712 One of the things that we held constant to move along 0:00:25.712,0:00:28.503 one demand curve, for the demand itself not to shift – 0:00:28.503,0:00:30.067 for the curve not to shift – 0:00:30.067,0:00:37.756 is price of related goods. [WRITING] 0:00:37.756,0:00:40.898 The other thing we assumed that's being held constant 0:00:40.898,0:00:45.764 is price expectations for our good. [WRITING] 0:00:45.764,0:00:48.176 And now we'll list a couple of them that are fairly intuitive. 0:00:48.176,0:00:49.762 But you'll see that in the next few videos, 0:00:49.762,0:00:52.717 that there are often special cases even to this. 0:00:52.717,0:00:55.344 So, the other thing that we've been holding constant 0:00:55.344,0:00:59.464 to stay on one demand curve is income. 0:00:59.464,0:01:01.192 And this one is fairly intuitive. 0:01:01.192,0:01:05.122 What happens if everyone's income were to increase? 0:01:05.122,0:01:07.712 And, in real terms, it were to actually increase? 0:01:07.712,0:01:08.682 Well, then, all of a sudden, 0:01:08.682,0:01:10.328 they have more disposable income – 0:01:10.328,0:01:12.636 naybe to spend on something like e-books. 0:01:12.636,0:01:14.670 And so, for any given price point, 0:01:14.670,0:01:15.940 the demand would increase. 0:01:15.940,0:01:18.380 And so, it would increase the demand. 0:01:18.380,0:01:20.109 And once again, when we talk about increasing demand, 0:01:20.109,0:01:22.931 we're talking about shifting the entire curve. 0:01:22.931,0:01:25.814 We're not talking about a particular quantity of demand. 0:01:25.814,0:01:30.014 So, income goes up, then [that] increases demand. 0:01:30.014,0:01:32.610 [WRITING] Demand goes up. 0:01:32.610,0:01:36.024 And remember ... when demand goes up, 0:01:36.024,0:01:37.084 we're talking about the whole curve shifting to the right. 0:01:37.100,0:01:38.901 At any given price point, 0:01:38.901,0:01:42.366 we are going to have a larger quantity demanded. 0:01:42.366,0:01:43.987 So the whole curve, 0:01:43.987,0:01:45.268 this whole demand schedule would change. 0:01:45.268,0:01:48.826 And likewise, if income went down, demand would go down. 0:01:48.826,0:01:49.872 And [as] we're going to see in a future video, 0:01:49.872,0:01:51.561 it's actually quite interesting, 0:01:51.561,0:01:53.428 that's not, always ... the case. 0:01:53.428,0:01:58.380 This is only true for normal goods. 0:01:58.380,0:02:00.533 [WRITING] "normal goods." 0:02:00.533,0:02:03.226 And in a future video we'll see goods called "inferior goods," 0:02:03.226,0:02:05.426 where this is NOT necessarily the case. 0:02:05.426,0:02:07.456 Or, by definition, for an inferior good, 0:02:07.456,0:02:09.820 it would not be the case. 0:02:09.820,0:02:12.138 Now the other ones that are somewhat intuitive 0:02:12.138,0:02:15.628 are population. [WRITING] 0:02:15.628,0:02:18.135 Once again, if population goes up -- 0:02:18.135,0:02:20.143 obviously -- at any given price point, 0:02:20.143,0:02:21.798 more people will want it. 0:02:21.798,0:02:23.397 So, it would shift the demand curve to the right -- 0:02:23.397,0:02:25.212 or it would increase demand. 0:02:25.212,0:02:28.888 If population were to go down, it would decrease demand, 0:02:28.888,0:02:32.201 which means shifting the whole curve to the left. 0:02:32.201,0:02:33.679 And then the last one we'll talk about -- 0:02:33.679,0:02:35.647 And remember, we're holding all these things constant 0:02:35.647,0:02:37.487 in order for demand not to change. 0:02:37.487,0:02:40.572 The last thing is just preferences. 0:02:40.572,0:02:42.078 We're assuming that people's tastes 0:02:42.079,0:02:43.752 and preferences don't change 0:02:43.752,0:02:46.903 while we move along a specific demand curve. 0:02:46.903,0:02:50.574 If preferences actually change, then it will change the curve. 0:02:50.574,0:02:56.484 So, for example, if, all of a sudden ... the author of [a] book 0:02:56.484,0:02:58.575 is on some very popular show -- 0:02:58.575,0:03:01.082 talk show -- that tells everyone 0:03:01.082,0:03:03.346 that this is the best book that was ever written, 0:03:03.346,0:03:05.302 then preferences would go up, 0:03:05.302,0:03:07.902 and that would increase the total demand. 0:03:07.902,0:03:09.516 At any given price point, 0:03:09.516,0:03:11.322 more people would be willing to buy the book. 0:03:11.322,0:03:13.665 If, on the other hand, on that same talk show, 0:03:13.665,0:03:16.160 it turns out that they do an exposé 0:03:16.160,0:03:18.617 on the author having this sordid past 0:03:18.617,0:03:20.486 and [they state that] the author plagiarized the whole book, 0:03:20.486,0:03:22.800 then the demand will go down. 0:03:22.800,0:03:25.050 The entire curve, regardless of the price point -- 0:03:25.050,0:03:26.429 at any given price point -- 0:03:26.429,0:03:32.380 the quantity demanded will actually go down.