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Pie charts are a widely and (often) inappropriately used form of data visualization. Their simplicity makes them appealing to visualize parts of a whole. However, pie charts are often misused, leading to the misinterpretation or distortion of data. Below, I’ll outline some common misuses of pie charts and offer practical suggestions for improving your data visualizations.

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Too Many Categories

A common misuse of the pie chart is presenting too many categories (or slices) in a single chart. Pie charts with numerous slices quickly become cluttered and difficult to read. This inhibits interpretation of the chart, making it impossible to discern between slices or to compare between slices accurately.

The Fix

If you decide to use a pie chart, consider grouping smaller categories or like categories together to reduce the number of slices in the pie chart and improve its readability. However, sometimes aggregating data together is not appropriate. For these data, consider bar and column charts as better alternatives, as they more effectively display categorical data.

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Close Comparisons

Pie charts are not well suited to presenting data requiring precise comparisons between categories. That is, slices that are close in size are difficult to distinguish between. This is because angles are more difficult to interpret (Skau, D. and Kosara, R., 2016) relative to lengths (e.g., as in the bars in bar charts).

The Fix

Bar or column charts are more suitable for visualizing close comparisons between categories. Bars allow for easier comparison, as the length of each bar is easily interpreted relative to distinguishing between similar angles in a pie chart.

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3D Pie Charts

Using 3D pie charts further distorts our ability to read them. The 3D perspective can make some slices appear disproportionately larger due to their relative position within the visual. That is, segments that are closer appear larger relative to slices farther back, regardless of their actual proportions.

The Fix

This fix is simple: do not use 3D charts. Standard 2D charts are superior in visualizing data (for all chart types, including pie charts) compared to 3D charts. Use 2D pie charts for easier interpretation.

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Unsorted Categories

Another issue in pie charts is when categories are plotted in a seemingly random order. Without the logical ordering of categories (e.g., largest to smallest) it becomes difficult to extract meaningful insights from the data.

The Fix

Ordering categories from largest to smallest improves the readability of pie charts. The intent is to draw attention to the largest categories first, which are often the most important.

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Non-Proportional Data

Pie charts are useful for visualizing the proportions of a whole. Using pie charts to visualize non-proportional data (i.e., proportions exceeding 100%) often leads to confusion as it is designed to represent a complete whole only.

*While identical in appearance, the above example illustrates how misleading non-proportional data are when visualized using pie charts. The first slice, 85%, clearly does not represent 85% of the total pie chart. Therefore, it is difficult to gain meaningful insights from a chart the requires the reader to both interpret the overall percentage of each slice and the relative proportion of each slice relative to the rest of the pie chart.

The Fix

Use alternative data visualizations, such as bar or column charts. These visualizations are better suited to display non-proportional data, as they show individual values without suggesting a proportional relationship between categories.

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Too Much Colour

Too much colour in a pie chart can detract from the message of the pie chart. Colour is important for distinguishing between slices, but its overuse can be overwhelming and hard to interpret. Additionally, certain colour combinations can be difficult to distinguish, especially for those with colour vision deficiencies.

The Fix

Use colour strategically to highlight the most important point in your pie chart. Applying muted tones, such as greyscale, to less relevant data allows the primary colour and key message to stand out allowing your pie chart to clearly communicate its main point.

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Final Thoughts

Pie charts can be effective when used appropriately. However, they are less effective in visualizing complex data or data requiring close comparisons. Before defaulting to a pie chart, consider alternative data visualizations (such as bar charts) that may be more suitable for communicating the message of your data.

The key to effective data visualization is clarity. Avoiding these common pie chart pitfalls and selecting the right chart type for your data will ensure that your visualizations communicate information both accurately and effectively.

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If you’re a program manager, you may be required, or better yet, want to evaluate your program. One of the first steps is identifying if you have internal evaluation capacity or require an external evaluator (Internal vs External Evaluators: What’s the Difference and Which One is Right for You?). In either case, evaluation can be an overwhelming prospect.

And that’s fair! Evaluation can be new, and you may not fully understand the process. Evaluations can be complex, with lots of moving pieces. It can be a challenge to navigate timelines and schedules, stay on top of various steps and phases, and make sure that everyone knows what they need to know.

Luckily, there are a few actions you can take to help yourself and your team prepare! These certainly aren’t mandatory, but you might find that these tips can help an evaluation stay on track and go a little smoother!

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Involve us early

Evaluation often comes up when a grant is wrapping up or a budget cycle is ending, but it can be harder to evaluate a program that is done or nearing completion. In fact, evaluators love when people have thought about evaluation early into a project, even right from the planning stages!

Being included early makes our jobs as evaluators easier, but it can also help you plan your program or initiative effectively and set yourself up for a successful evaluation. Starting early means you can adjust your program in response to feedback, collect baseline information, and implement procedures to gather other useful data. It also gives you a great opportunity to conduct other types of evaluation than summative, like formative evaluation, process evaluation, developmental evaluation, or participatory evaluation.

Even if your program is already underway, it’s not too late! You can start planning to evaluate as soon as you think of it. Evaluation can still help you gather feedback, make changes, and demonstrate the effectiveness of your program (if you want to apply for a grant, for example).

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Consider your goals

Reflect on what you hope to learn by evaluating your program. The clearer you are about your goals, the more you’ll be able to act on the findings. Check out this infographic for 10 reasons why you might want to evaluate.

You might also want to consider what you plan to do with the results. What will you share with leadership, staff, and the public? Are you hoping to adjust your processes, or tell a story about the impact of your program? Knowing what you want to do with the results will help your evaluator collect the right data and craft reports or other products that meet your needs!

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Help us understand

To be effective in our roles, evaluators need to have certain information about the program or initiative being evaluated. Having an understanding of the program, key partners, and goals of the evaluation will help at every stage of the process. For internal evaluators, this may be a simple process, as they likely have some familiarity already. Sharing information is even more relevant if the evaluator is external. When the evaluator has a good understanding of the program and its context, they can help ensure that the evaluation turns out useful and presents valuable insights for you.

We’ve written about this on Eval Academy before, so definitely check out this article to read more about what information you should be prepared to share with an evaluator.

How you share this information can be flexible. If you don’t have existing documents that perfectly summarize everything, just be prepared to share it verbally during a meeting!

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Engage staff and other partners

In our work at Three Hive Consulting, we typically involve various partners in the evaluation process; we ask for representatives from various departments or roles. While it does depend on what you’re hoping to gain from the evaluation, we often like to speak with staff, clients/patients, and organizational partners. We can capture valuable insights by gathering thoughts and feedback from people that are involved in the program or initiative in different ways.

Making sure that these partners are aware the evaluation is occurring and that they might have an opportunity to be involved can make data collection easier. Even if specific dates haven’t been established yet, letting people know ahead of time that they’ll be invited to participate in surveys, interviews, or focus groups can give people time to get used to the idea and ensures that the invitation won’t be a confusing surprise! We often ask representatives to be the champions of the evaluation, encouraging others to participate in data collection.

Continuing to engage with staff and other partners throughout the entire process can also encourage interest in the evaluation and its results, and support the adoption of changes afterwards.

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Think about data

Evaluators also often make use of existing data that has already been collected. These can look like intake forms, participant data, meeting minutes, facilitator notes, annual reports, and previous evaluations. You can begin to take stock of available data even before the evaluation kicks off. You might even start identifying potential difficulties in accessing data, like privacy procedures or the format and location of files.

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Think about obstacles early

Because the data collection phase often involves several different groups of people, the logistics can be tricky; this sometimes causes delays in the evaluation. Planning for these challenges can support more efficient and timely data collection. You can start to discuss potential barriers with your evaluator early on—like team capacity, conflicting schedules, and missing contact information—and then collaborate on a plan to address them!

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Communicate often

Last, but certainly not least! Regular communication should occur at every stage of an evaluation, and all parties, including evaluators, program managers, and evaluation committee members, play a role in making this happen!  Be prepared for meetings or regular touchpoints with your evaluator. They will require your time to explain processes or feasibility, to review and approve plans or data collection tools, and to offer your insights. If capacity is an issue, one strategy is to identify other decision makers who can represent your program.

Effective communication can help avoid misunderstandings, circumvent obstacles, and keep an evaluation on track. Proactively identifying and communicating an issue gives everyone time to strategize or shift approaches. It also gives you and your team a chance to provide context on emerging findings or give feedback on deliverables. For Three Hive’s projects, we tend to set up biweekly or monthly meetings to establish an opportunity for everyone to share updates and exchange feedback.  

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Keep learning about evaluation

Evaluation-focused content is often directed at evaluators, but that doesn’t mean that non-evaluators don’t have an important role to play in supporting the success of evaluations! We hope these actionable tips help you feel more confident and prepared for the next time you’re involved in an evaluation!

For more in-depth training in evaluation, our Program Evaluation for Program Managers course has been developed for program managers like you.

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If you’re new to evaluation, check out these other articles and resources:

Infographic: A Beginner’s Guide to Evaluation: A summary of introductory resources for new evaluators — Eval Academy

Common Evaluation FAQs — Eval Academy

Evaluation as self-care for your program — Eval Academy