Economics · Ch 1 — Graphs in Economics
Diagrammatic Presentation: Bar Diagrams and Pie Diagrams
Diagrammatic Presentation: Bar Diagrams and Pie Diagrams
Bar Diagrams
A bar diagram represents data using a series of bars (rectangles) of equal width, with the height (or length) of each bar proportional to the value it represents. The bars are usually drawn with uniform spacing between them, and the diagram carries a scale showing what one unit of height stands for.
Common types:
| Type | Used when |
|---|---|
| Simple bar diagram | One variable is compared across categories (e.g., population of five districts) |
| Multiple bar diagram | Two or more related variables are compared side by side for the same categories (e.g., exports and imports over several years) |
| Sub-divided (component) bar diagram | A total is broken into its components, each bar stacked in segments (e.g., total revenue split into tax and non-tax revenue) |
Pie Diagrams
A pie diagram (or pie chart) represents the components of a total as sectors of a circle, where each sector's angle is proportional to its share of the total. Since a full circle measures 360°, the angle for any component is found as:
Pie diagrams are best suited to showing composition (how a whole splits into parts) rather than trend over time — for that, a line graph (Section 3) is the better tool. …
A diagram using bars of equal width, whose height (or length) is proportional to the value b …
A diagram representing the components of a total as sectors of a circle, each sector's angle proportional to its …