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Lesson 4: Demand

# Changes in income, population, or preferences

In this video, we explore how changes in a few factors affect the demand curve. Changes in income, population, and consumer preferences cause the entire demand curve to shift.  Created by Sal Khan.

## Want to join the conversation?

• So therefore, something that is free would have infinite demand? Such as khan academy?
• No; because the market, though relatively large, is definitely finite. As price drops, the market could tend towards saturation rather than infinite demand.
• I am really getting into preparing for my economics course in the fall. Has anyone found good practice problems/tests to supplement the microeconomics videos?
• Yep- that's the point of an advertisement. They try to change consumer preferences and create desires that otherwise wouldn't have been realised.
• Hey Sal, big fan of this particular series. But I've got a minute question for this video, specifically about the population and the income. If the population goes up, then there'll be more people who would want your product; but if there are more people, wouldn't that mean that everyone has less income? And if population increases, then the "newer" population will be children. Wouldn't children take away some of that disposable income from their parents? Thanks in advance!
• This is a good question. But there is one thing that you understand wrong about "population".

I think when he said "population", he means "community" and population increases = bigger community . Time helded constant
• i want to ask a question to the author .why the population income affects demand and the poulation affects demand?
• Population income affects the demand because the more money people have the more money their going to be willing to spend and the more their going to buy.
The actual population changes the demand simply because when there are more people more units will be bought.
• Sal, I did the math, and as you raised the book price, even taking into account the lesser amount of people, one trend i saw, was that the your profit went up, even as the number of people buying the book drooped, was that intended or not?
-Darth Revan
• Though Sal's example seems consistent with what we see in reality. We cannot calculate profit in the absence of cost data. We can't say much about profit, without knowing the cost of managing licenses or server space/access for these files.
• wut if u have infinite supply? Will u get infinite money?
(1 vote)
• Economics deals with situations of scarce resources. If you have infinite supply you are in another realm!
• I usually here from politicians about how prices for things are going up while income is staying the same; are incomes and prices related in such a way that incomes should increase as things are getting more expensive?
• It should be realated. If not, the families will not buy as much goods as the year before. That results in a decrease of demand.