Pie Charts

Comparison of Search Share, September and October 2009

Monday, November 30, 2009 by Jon Peltier 10 Comments

Monday, November 30, 2009 by Jon Peltier
Peltier Technical Services, Inc., Copyright © 2023, All rights reserved.

The Marketing Charts blog compared Google to the rest of the world in Online Search Share, September 2009 & October 2009. The “guidelines” were followed: for parts of a whole, use a pie chart. And for comparison, why not two pies side by side?

September 2009 Online Search Pie Chart October 2009 Online Search Pie Chart

Well, as Edward Tufte once said, “The only thing worse than a pie chart is several of them.” Especially in this case. If not for the different titles and the percentage data labels, I would think someone had goofed and used the same graphic twice.

Having to read the numbers off the chart to make comparisons defeats the purpose of graphing the data, but is not as efficient as a table, because the numbers are strewn about the visual field. I can see that Google takes up most of both pies, but I can only estimate that Google’s take is about 2/3 of either pie.

So what are we trying to show here? If we want to show how each search engine’s share changed, a clustered column chart is good, because the two bars for each company are adjacent, for easy comparison.

September and October 2009 Online Search Column Chart

It’s easy to see that Google and Microsoft both went up slightly, and Yahoo went down. And nobody’s really concerned with AOL or Ask, are they?

An alternative to the column chart is a line chart. I shaded the plot area light gray, so it’s obvious that even though Google is way up here and the rest are way down there, all are part of the same chart.

September and October 2009 Online Search Timeline

Again, it’s clear that although the changes were rather small, Google and Microsoft both gained at the expense of Yahoo.

What if it’s the change itself that we want to show? Again, a column chart fits the bill.

Change in Online Search from September to October 2009

There are a lot of options when you’re selecting the chart type. You need to decide what you want to show in your chart, then select an appropriate graphic that shows it. As usual, it’s not a bad move to select from the array of 2D line and bar charts.

And I had too much pie over the Thanksgiving weekend. They call it a long weekend, when a more accurate phrase would be wide weekend.

Posted: Monday, November 30th, 2009 under Chart Busters.
Tags: Column Charts, Pie Charts.
Comments: 10

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NPR Analysis by Chart Busters

Friday, September 11, 2009 by Jon Peltier 10 Comments

Friday, September 11, 2009 by Jon Peltier
Peltier Technical Services, Inc., Copyright © 2023, All rights reserved.

Last spring, FastCompany published an analysis of National Public Radio, which has taken off in the past decade. Will NPR Save the News? discussed NPR’s revenues and compared its audience with that of two other major news outlets, newspapers and television news.

Yeah, NPR is great and all, I even listen occasionally. But this is a Chart Busters column, so I’m going to talk about the visualizations that accompanied the FastCompany article. Specifically I want to draw attention to the following two graphs.

FastCompany Graphical Analysis of NPR

Look at the first graph: it’s a pie chart, in 3D, not only exploded, but with the pieces rearranged. At least they’re in order, but how are we supposed to interpret it?

You could put the pie back together, and take a bird’s eye view.

NPR Revenue Pie Chart

Yeah, not much better, but at least we’re not distracted by the thickness. The pie isn’t really much different than a set of labels. Here is the misaligned non-tabular table that results when we hide the pie pieces.

NPR Revenue Labels

Time to revert to an old standby. This bar chart clearly shows the relationships between the five revenue sources, and if we look very carefully at the Y axis labels, we see that they are formatted as percentages, so it’s no huge jump to realize they all add to 100%.

NPR Revenue Bar Chart

The revenue data isn’t all that fascinating, but the audience statistics tell an interesting tale.

The second FastCompany graph is another 3D wonder, a bar chart rendered in isometric view. The angles make the bar comparisons difficult, and also make the labels less readable than if they’d been printed straight. And in fact, the use of huge bars for percent change in audience takes away any analysis of audience size itself, which is an interesting variable in its own right.

Let’s compare the audience sizes. In this line chart we can tell at a glance that NPR as increased greatly, while TV and newspapers have gone down.

NPR Audience Line Chart

This stacked bar doesn’t show the relative audience sizes as clearly, but it shows that the overall audience has declined a bit, and we can still tell that NPR’s audience has nearly doubled.

NPR Audience Stacked Chart

We can compare share of the market, that is, share of the total audience. Again, in this line chart, the trend over the past decade is clear. NPR’s share has doubled at the expense of newspapers and especially television.

NPR Market Share Line Chart

A stacked bar chart of audience share shows much the same trend.

NPR Market Share Stacked Chart

There are obviously more than three sources for news. Newspapers and television stations have web sites, and there are numerous blogs reporting news. I would think overall that the audience is much greater than the approximate 100 million shown in my first line chart.

The decline in television news is not surprising, and I’m sure the television outlets are not too worried. They have plenty of so-called reality programming now, which is cheap to produce and generates huge advertising revenues.

From all of the gloom and doom stories, I would hve expected to see a much greater decline in newspaper audience. I no longer get a daily paper, and in many cities, the number of major papers has declined. If we re-examine these numbers in five years, we may see another 11% drop in newspaper audiences.

Posted: Friday, September 11th, 2009 under Chart Busters.
Tags: 3D Charts, 3D Pie Charts, Pie Charts.
Comments: 10

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Simple Bar Chart Beats Complex Multiple Sized Pies

Monday, August 31, 2009 by Jon Peltier 11 Comments

Monday, August 31, 2009 by Jon Peltier
Peltier Technical Services, Inc., Copyright © 2023, All rights reserved.

An Excel user asked how to produce pie charts of different sizes, so that the total of the wedges comprising each pie dictates its size. The idea behind the different sized pies is to provide a qualitative display of the whole pies and the individual wedges.

I pointed out the generally poor ability to judge areas, and proposed a bar chart alternative that provides not only a qualitative3 display, but also a quantitative display.

The user posted the following sample data showing the hourly costs of operation of three conveyors, broken down into four constituent cost elements.

Data for Conveyor Operating Costs

The user envisioned a display of pie charts similar to the following. Conveyor 2 has the greatest costs. Conveyor 1 has the lowest costs, only 35% that of Conveyor 2, and Conveyor 3 has nearly the same costs, 43% those of Conveyor 1. If we make the area proportional to cost, the diameter of the pies will be proportional to the square root of cost, so Conveyors 1 and 3 have pies with diameters 59% and 65% as large as that of Conveyor 2.

Pie Chart of Conveyor 1 Operating Costs Pie Chart of Conveyor 2 Operating Costs Pie Chart of Conveyor 3 Operating Costs

You can see that Conveyor 2 is the most expensive to operate, and you may get a sense that conveyor 1 is the cheapest. But it is at best a qualitative view. You cannot easily compare the magnitudes of the operating costs of the conveyors. You can roughly judge that Power is a somewhat larger proportion of Conveyor 2’s operating costs, but you cannot compare the relative costs of operator and parts.

The ineffective comparisons offered by the pie charts can be fixed by using a single bar chart. In fact, a simple clustered bar chart is sufficient, with one cluster per conveyor showing the total and constituent costs of operation. We can readily compare the total costs of operation, and we can see that the costs of operator and parts make up only a tiny and nearly invariant portion of the total.

Bar Chart Comparing Conveyor Operating Costs

Some labeling of the bars can help if we need to show precise values or percentages. The total bar labels below show simply the corresponding values, while the percentages of the other bars have been computed in the worksheet, and added to the bars using Rob Bovey’s free and indispensable Chart Labeler add-in.

Labeled Bar Chart Comparing Conveyor Operating Costs

Posted: Monday, August 31st, 2009 under Chart Types.
Tags: Bar Charts, Pie Charts.
Comments: 11

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Which Pie is Better?

Saturday, August 1, 2009 by Jon Peltier 7 Comments

Saturday, August 1, 2009 by Jon Peltier
Peltier Technical Services, Inc., Copyright © 2023, All rights reserved.

In Whacky Graphics at USAspending.gov, Seth Grimes of Intelligent Enterprise (another Seth G) deconstructs a pie chart showing Federal Spending FY 2009 on USAspending.gov’s interactive dashboard. As Seth says, this is “one downright whacky graphic. I can’t recall the last time I saw a graphic that so distorted the numbers, so I tried to recreate it (and failed).”

So what’s wrong with the chart?

Whacky Pie Chart at USAspending.gov

Seth says, “Now I’m not a big believer in 3-D charting that simply adds depths, supposedly creating visual appeal, to a 2-D chart.” As you all know, neither are we here at Chart Busters, Inc. And of course, adding 3D effects to a pie chart is adding insult to injury.

There’s an interesting negative value, Loans, in the table below the chart. It may or may not have been added to this chart, but since it comprises less than 0.01% of the total, it isn’t visible, and they mercifully did not label it. We have seen in Pie for Dessert Again? that Excel allows negative numbers in pie charts, and merely plots their absolute values. Makes perfect sense.

Seth also asks us to ignore the labels for a moment, and judge which area is largest: the purple wedge in the front right of this ugly ovoid, the brick red wedge at the left. or the combined orange and blue wedge in the top right? To my untrained eye, they look about the same. But the labels show that these areas represent 38%, 47% and, 14% of the total. As Seth points out, this is not just caused by the magical distortion of 3D rendering, but also because the numbers don’t agree with the graphics.

We’ve also seen in Pie Chart Plotting Deficiency that even Microsoft doesn’t always care that numbers in pie charts add up. But the Microsoft chart merely left off the “Other” category, while the USAspending chart is just way off.

Seth made a 2D chart to show a more accurate depiction of the data. Note that he included the Loans wedge, but it’s not even as thick as the leader line attached to the data label.

More Accurate 2D Pie Chart by Seth Grimes

Then Seth tries to reproduce the 3D appearance of the original chart, and he almost succeeds, except that his numbers are still faithful to the inputs.

More Accurate 3D Pie Chart by Seth Grimes

Seth has demonstrated without doubt that the original pie was doctored. He suspects that at some point after the chart was constructed, the site design was turned over to a graphic artist who “improved” the display. Seth hasn’t demonstrated that 2D or 3D pies are a good way to illustrate this information. Okay, chart busters, what’s the best way to show this kind of data?

A boring. old. bar. chart.

I’ve made two versions, one with the minuscule Loans category:

Better Bar Chart by Chart Busters

and one without:

Better Bar Chart by Chart Busters

Seth’s planning a review of the USAspending.gov dashboard. I’m looking forward to that. I spent a few minutes on the dashboard, and found it awkward, with labels scrolling out of view before you could read them.

Posted: Saturday, August 1st, 2009 under Chart Busters.
Tags: Pie Charts.
Comments: 7

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Political Pie Charts

Monday, July 20, 2009 by Jon Peltier 13 Comments

In the wake of the Mark Sanford scandal, in which the South Carolina governor was accused of hiking in the Andes with his mistress or something, political blog FiveThirtyEight has published results of surveys about Sanford in Should Sanford Resign?. I was pointed to the FiveThirtyEight survey results by Andrew Gelman in Doing graphics the George Orwell way, and he got it from Should Mark Sanford Resign?. Andrew’s take is that the pie charts used by FiveThirtyEight to present the survey results weren’t as bad as they first looked.

Polling and Election Results on FiveThirtyEight

I’ve stated in this blog that the FiveThirtyEight web site uses pie charts in a very effective way. It helps that there are only two or three segments in their pies, and the third, if present, is very small. Here is a partial view of the FiveThirtyEight analysis of the November 2008 US elections.

FiveThirtyEight Pie Charts of 2008 US Election

This isn’t a full-blown Chart Busters article, but I thought I’d discuss some alternatives.

In an unfinished post from last fall, I undertook to replace FiveThirtyEight’s pies with bars, using roughly the same amount of space. The bars may have slightly better resolution, but I didn’t include a third bar for the third tiny segment. Take your pick.

Jon's Bar Charts of 2008 US Election

Survey Results

FiveThirtyEight used pie charts to illustrate the survey results. As every second grade student will tell you, pies are the chart of choice when showing parts of a whole. The educational system has trained our children to behave like sheep, and follow the herd.

Editorializing aside, these charts of the poll results are what motivated this post.

Is Mark Sanford more or less ethical than other politicians?

FiveThirtyEight didn’t even change the Excel defaults for their pie. Black chart border, ugly fill colors, and way more space everywhere than needed, especially on either side of the chart. It’s nice that the data points are labeled, but they are only partially labeled with the percentages, and the reader still must journey back and forth to the legend to see which segment means what. I also think it’s useful to put the results of a poll not in numerical order (55%-18%-18%-9%) but in some value order of the categories (more-same-less).

FiveThirtyEight Pie Chart Results of Poll on Mark Sanford's Ethics

I have redesigned the pie chart, shrinking the white space and using arguably better colors. I also reordered the points, and centered the chart differently to try to make comparisons easier.

Jon's Redone Pie Chart Results of Poll on Mark Sanford's Ethics

All well and good, but without the percentages, it’s still a guess whether More or Less had a greater response.

So I pulled a bar chart out of my magic hat. We can see that most of the cynical poll responders think Sanford’s ethics are no different than the other politicians, and equal numbers thought he was more ethical and less ethical. 9% have been busy watching Real Housewives and don’t know who Mark Sanford is.

Jon's Bar Chart Results of Poll on Mark Sanford's Ethics

Should Mark Sanford Resign?

FiveThirtyEight used another pie to show whether respondents want Sanford to resign. The colors have been changed from the gruesome defaults, but the large wasted spaces remain, as does the legend and border. Also, FiveThirtyEight didn’t use its usual style where competing results A and B meet at the vertical line at 12 o’clock.

FiveThirtyEight Pie Chart Results of Poll on Whether Mark Sanford should Resign