Graphing the Demand Curve

Before we can draw, we need data. A Demand Schedule is a simple table that shows how much of a product people are willing to buy at different prices. It follows the Law of Demand: as the price ($P$) of a good increases, the quantity demanded ($Q_d$) decreases. Think of it like a 'price-to-desire' list. If a candy bar is $\$0.50$, you might buy 4. If it jumps to$\$5.00$, you might buy 0. This inverse relationship is the foundation of all market graphs. In your table, you will always have two columns: one for Price and one for Quantity.

To turn our table into a graph, we use a coordinate plane. In economics, we have a very specific rule for where things go. **Price ($P$) always goes on the vertical Y-axis, and Quantity ($Q$) always goes on the horizontal X-axis**. A great way to remember this is that the letter 'P' is tall and points up to the sky! Each row in your demand schedule becomes a single coordinate point on this graph. Instead of $(x, y)$, we think of them as $(Q, P)$ points.

Once your points are plotted, you connect them with a straight line or a smooth curve. This line is called the Demand Curve. Because of the Law of Demand, this curve will almost always slope downward from left to right. We label this line with a capital $D$. This visual tool is powerful because it allows you to estimate demand for prices that weren't even on your original table. If you look at the line between your points, you can 'see' the behavior of the entire market at a glance.