A graph representing individual demand curve shows the quantity demanded at each price. The graph plots Quantity along the horizontal axis and Price along the vertical axis. A curve with a negative slope is plotted on the graph with two points marked on it, one to the top left of the curve, the other to the bottom right. A callout pointing to the first point marked on the curve reads, The first few items yield a higher marginal benefit, and so you would buy even at a high price. A callout pointing to the second point marked on the graph reads, But at a higher quantity, each extra item yields a low marginal benefit, and so you would only buy at a low price. Beside the graph, the rational rules for buyers are listed as follows: Buy more of an item if its marginal benefit is greater than (or equal to) the price; Price equals marginal benefit; Your demand curve is your marginal benefit curve; and Your demand curve is downward sloping because of diminishing marginal benefits. The third rule points to the two points marked in the graph.

A text box titled Market Demand Curves lists the following:

1, Survey a representative sample of the market, asking people the quantity they will buy at each price.

2, For each price, add up the total quantity demanded by the people surveyed.

3, Scale up the quantities demanded by the people surveyed, so that they represent the entire market.

4, Plot the total quantity demanded by the market, against price.

A graph below the text box is titled When the price changes: Movement along the demand curve. The line graph plots Quantity along the horizontal axis and Price along the vertical axis. A curve with a negative slope has two points marked on it. A downward arrow between the two points represents a price cut causing a rise in quantity demanded. An upward arrow between the two points represents a price rise causing a decline in quantity demanded. A bidirectional arrow between two points along the horizontal axis that correspond to the points marked on the curve represents a change in the quantity demanded. A bidirectional arrow between two points along the vertical axis that correspond to the points marked on the curve represents a change in the price. Another line graph is titled When other factors change: Shifts in the demand curve. Three curves with negative slopes run parallel to each other. A rightward arrow from the second curve to the third represents the following:

An increase in demand may reflect:

1, Increased income (if normal) or decreased income (if inferior)

2, Preferences shift to this good

3, Decreased price of complements or increased price of substitutes

4, Increased expected future price

5, Decreased congestion or increased network effects

6, Increased types of buyers changes or in number of buyers

A leftward arrow from the second curve to the first represents the following:

A decrease in demand may reflect:

1, Decreased income (if normal) or increased income (if inferior)

2, Preferences shift away from this good

3, Increased price of complements or decreased price of substitutes

4, Decreased expected future price

5, Increased congestion or decreased network effects

6, Decreased types of buyers changes or in number of buyers.

Text below this list reads, The acronym P E P T I C can help you remember these six shifters.