Comprehensive Notes on Demand, Supply, and Elasticity

Definition: A Latin term meaning "keeping everything else constant" or "all other things being equal." It is a crucial assumption in economics, not an economic term itself.
Application: In the context of demand, it implies that when observing the relationship between price and quantity demanded, all other factors that could influence demand (like income, preferences, etc.) are held constant.
Significance: Allows economists to isolate the effect of a single variable, such as price, on another variable, such as quantity demanded.

Relationship: There is an inverse relationship between the price of a good and the quantity demanded. As price goes down, quantity demanded goes up; as price goes up, quantity demanded goes down.
Explanation: Consumers generally demand more of a good at a lower price than at a higher price.
Demand Schedule/Table: A table that shows the relationship between the price of a good and the quantity demanded (under the assumption of ceteris paribus).
Demand Curve: A graphical representation of the demand schedule. It always slopes downwards from left to right due to the law of demand. For simplicity, a linear function is often assumed.

Individual Demand Curve: Represents the quantity of a good a single consumer is willing and able to buy at various prices.
Market Demand Curve: Derived by adding up all the individual demands for a good at each and every price level. This is a horizontal summation of individual demand curves.
Example: If at ext{40 extcent}, Customer 1 demands 6 units and Customer 2 demands 2 units, the market demand is 6 + 2 = 8 units.

Real-world data often supports the theory of an inverse relationship between price and quantity demanded.
When plotting data points (high price, low quantity demanded; low price, high quantity demanded), a line of best fit naturally resembles a downward-sloping demand curve.

Change in Quantity Demanded: This refers to a movement along the existing demand curve. It is caused solely by a change in the price of the good itself.
- Example: If the price of a pizza decreases from ext{ extdollar}15 to ext{ extdollar}10, the quantity demanded increases from 6 to 10 (moving from point A to point B on the same curve).
- Historically, this was sometimes called an "expansion" or "contraction" in demand.
Change in Demand: This refers to a shift of the entire demand curve (either to the left or right). It is caused by a change in any factor other than the price of the good.
- Mechanism: A