Pie Charts: Reviving Their Usefulness in Data Visualization

Introduction

Pie charts, often maligned for their supposed shortcomings, are frequently criticized for not revealing exact values, showing changes over time, or illustrating key assumptions, causes, or patterns. Despite these assertions, pie charts remain a handy tool for illustrating numerical proportions and providing quick insights. Their versatility and ease of use make them a preferred choice for many data visualization tasks.

When Pie Charts Shine

To my mind, pie charts are not as terrible as many believe. They bring distinct advantages to the table when used appropriately for the right context. Here are some key points supporting their use:

Convenience in Proportional Comparison

Pie charts are particularly useful when you need to quickly assess the proportions and percentages between categories. Each slice represents a percentage, making it easy to identify which category has the highest or lowest share. This intuitive approach makes pie charts a valuable tool for visual storytelling in data analysis.

Reputation and Common Misuses

It's worth noting that pie charts often get a bad reputation because they are misused. Bad pie charts are a result of poor design and excessive complexity. A well-designed pie chart with a limited number of slices can be an effective way to convey information. However, when pie charts have too many slices or categories, it becomes difficult to discern the differences between them. In such cases, alternative chart types like bubble charts or proportional area charts can provide clearer insights.

When Not to Use Pie Charts

While pie charts can be effective, there are scenarios where they fall short and alternative chart types are more suitable:

Data with Many Categories

When dealing with more than six categories, a pie chart can become cluttered and difficult to interpret. In such situations, consider using bar charts or dot plots. These alternatives can better convey the relationships between categorical data without the confusion that comes with too many slices.

Best Practices for Pie Charts

To ensure that pie charts serve their purpose effectively, consider the following best practices:

Limit Slices

Keep the number of slices limited to six or fewer. This helps maintain clarity and avoids the issue of comparing multiple angles simultaneously. Each slice should represent a meaningful category, and too many can dilute the impact of the data.

Use Clear Labels

Proper labeling is crucial. Each slice should be labeled with the category name and the percentage it represents. Avoid having too many labels, as this can clutter the chart and reduce readability.

Choose the Right Color Scheme

A well-chosen color scheme can enhance understanding. Use a consistent and distinct color for each category to avoid confusion. Avoid color schemes that blend or create contrast too sharply, as this can hinder the reader's ability to distinguish between slices.

When to Avoid Pie Charts

While pie charts have their place, they are not always the best choice depending on the data and context. Here are some scenarios where you might want to opt for other chart types:

Comparing Data Across Multiple Charts

Pie charts can be difficult to compare across different charts. When you need to make direct comparisons over time or across different datasets, consider using bar charts, line charts, or stacked bar charts. These types of charts are designed for such comparisons and can provide a clearer visual representation.

Conclusion

In summary, pie charts have their place in data visualization. They are effective for quick, proportional comparisons and can be a valuable tool when used appropriately. However, it's important to be mindful of potential pitfalls. By adhering to best practices and understanding when to use them, pie charts can continue to be a useful tool in your data visualization arsenal.

References

For a deeper dive into the nuances of using pie charts, consider exploring the following articles:

Pie Charts When to Use a Pie Chart