Small multiple

Small multiples (a term popularized by Edward Tufte in "Envisioning Information") are a series of small similar pictures, making a point through repetition. As Tufte writes:

:At the heart of quantitiative reasoning is a single question: "Compared to what?" Small multiple designs, multivariate and data bountiful, answer directly by visually enforcing comparisons of changes, of the differences among objects, of the scope of alternatives. For a wide range of problems in data presentation, small multiples are the best design solution.("Envisioning Information", p. 67)

Example

In the example, the departmental salary expense is charted by month with a dashed line indicating the average for each department. The scales on each panel are different to emphasize the relative change over time compared to the range. Standardizing the scales could provide insight into comparisons in magnitude between the different departments.