Which visualization type is least effective for displaying change over time?

The pie chart is least effective for displaying change over time because it is inherently designed to represent parts of a whole at a specific point in time rather than illustrating trends or changes across multiple time periods. Pie charts provide a static snapshot of data distribution, making it difficult for viewers to discern how values change or fluctuate over time.

In contrast, line and area charts are specifically designed to show trends and changes over time, emphasizing the continuity of data points. Bar charts can also effectively display changes over time, especially when comparing distinct time periods side by side. Therefore, pie charts do not have the capacity to represent temporal dynamics, making them the least suitable option for this purpose.