There was a time when I wanted to use pie charts for everything. They looked great and they showed data with great clarity. But now if you google “pie charts are the best” , the first article that pops up is titled – “Pie Charts Are the Worst” and the search result went to the extent of calling them ‘Evil’! This is when I realized that I used pie charts only for percentages with not more than 3-4 pieces in one chart, and this was 10 years ago.
Below visualization is part of an article which talks about the employment growth of G-7 countries after the great recession. The two pie charts were originally part of a report released by the Council of Economic Advisers under the Obama Administration, to support that fact that the United states created more employment than all the other of G-7 combined since 2010. In other words, the rebound of the US economy was much faster than other advanced economies.
At first I really liked this visualization. The things which are working well are:
- The visualization is quite crisp. It clearly states that the chart on the left shows share of total employment for each of G-7 countries, and the right one shows the net employment growth. One can confidently claim that the charts talk about the 7 countries and comparatively the US is doing much better than others, which is the essence of the article.
- There is a clear mention of what time range is considered for the data used, validating the fact that the time after the recession of the late 2000’s is in consideration.
- The sequence of countries are same in both charts with names labelled. This makes it visually easier for the user to compare each country for its total and new employment growth
- A note is pro-actively added about rounding explaining that components may not sum to totals.
- Source citation is also one of the best practices which is not followed much but in this case it is clearly stated.
- There is no data overflow.
But going back to what I started with, pie chart is a great visualization technique when there is a need to show how a whole picture of is segmented (into few parts). The data sets for which pie charts are really helpful are the ones:
- which can be condensed to exact percentages.
- which do not break into more than 3-4 pieces.
Keeping this in mind, the things which could be improved in the above charts are:
Titles and Labels:
- One needs to read the whole article to realize that the claim of the visualization validates the title. The visualization lacks a more suggestive title.
- The time range is same for both the charts but still mentioned thrice (redundant). The space could have been used for the title.
- The sub-title has “percent” mentioned to show that the numbers are in-fact percentages, “%” sign next to the number would have served the same purpose and would have made easily readable along with saving the space.
- When pie charts have more than 3-4 pieces it becomes really difficult to tally the slices with the legend to identify which slice represents what. Therefore labeling is done for every piece (Country name and percentage in this case).The is of course across the entire chart (given it is circular) making it look messier.
Data Layout:
- Although countries have the same sequence in both charts, ordering them in ascending percentages would have been a better choice.
- The choice of slice colors could have been more pleasant, right now it looks too stark.
If I had to make this visualization, it would look like this .
Learning from the class:
- A visualization needs a clear context and claim to make it more independent. This helps user get the crux of the subject without actually reading the article created around it.
- Judicious choice of graph/chart is critical in terms of user friendliness and aesthetics. In this case a bar graph serves a better purpose than a pie chart:
- Comparisons become much easier.
- Data is not cluttered all across the visualization.
- Lesser labeling is needed.
Reference:
Business Insider Article: http://www.businessinsider.com/us-economy-added-jobs-faster-than-all-g7-economies-combined-2017-1
Report: https://obamawhitehouse.archives.gov/blog/2017/01/06/eight-years-labor-market-progress-and-employment-situation-december
Opinions about Pie chart and alternatives: https://www.quora.com/How-and-why-are-pie-charts-considered-evil-by-data-visualization-experts