I was recently asked my opinion of David McCandless’ chart “The Billion Pound-O-Gram,” pictured below.
The person who asked the question was impressed with this chart the first time he saw it. For this reason, he thought that I might find it an effective exception to McCandless’ other work. I do not.
This chart originally appeared in the Guardian on November 7, 2009. It was framed by the following explanation:
Huge sums of money are being bandied about and no-one knows what they are. It’s time to put them into perspective.
289 billion spent on this. 400 billion spent on that. When money reaches this level it literally becomes mind-boggling.
Yet these figures are regularly issued by the government - and the media - as if they are self-evident facts that everyone understands.
Frustrated by this, I created The Billion Pound-O-Gram.
I’ve mixed up of 2008/09 figures from the Treasury and the Guardian. Visualising the numbers like this puts them in visual context, making them easier to relate to.
I was pretty shocked by the size of the UK budget deficit - essentially the country’s overdraft. It’s more than an entire year’s worth of income tax.
A second chart appeared following this explanation to illustrate how the “top five ideas for plugging the deficit” offered by political parties in the UK might reduce it. To sum up, the story is that the UK’s budget deficit is really big, which McCandless tells by comparing it with other amounts of money that are apparently familiar to Guardian readers. The question that concerns us here is, “Does this chart tell the story effectively?” Does it put the budget deficit into perspective in a way that doesn’t boggle the mind as McCandless suggests? This is journalism, so the objective is to inform, to help readers clearly understand the size of the deficit.
By using rectangles of varying sizes arranged as a treemap of sorts, McCandless forces us to perform a perceptual task that we can’t do well (that is, area comparisons). This is a bad choice when he could have used a bar graph instead and allowed us to compare the lengths of bars that share a common baseline, which we can do exceptionally well. Furthermore, his arrangement of the rectangles is arbitrary—not based on category or on the sizes of values—which compounds the difficulty.
To better understand what I’m saying, try to answer the following questions without reading the numbers that appear in the rectangles:
- Which represents a larger amount: Mortgage Lending 2007 or NHS?
- How much greater is Mortgage Lending 2007 than State Pensions?
- Does State Pensions compared with Tesco Revenue look like the difference between 62 and 59, or much greater?
- Which is bigger: Income Support or Police?
You might argue that these comparisons aren’t critical to the story, which is primarily about the budget deficit. If we concern ourselves only with comparing the deficit with other values, nothing about the chart’s design makes this easy, even when items are adjacent to one another. For instance, try answering the following questions:
- How much greater is the deficit than Africa’s entire debt to Western nations, which appears immediately below it? (And don’t cheat by reading the numbers.)
- How much greater is “Bailout: Asset Purchasing and Lending” than the deficit?
- How does Income Tax compare to the deficit?
Without reading the numbers, you’re forced to make wild guesses, which are considerably different from the truth, which could have been presented clearly.
All of these comparisons are incredibly simple to make using the bar graph below. Take a minute to notice how easy it is to see the relationships between these values from largest to smallest and to compare them. Notice especially how easy it is to compare each of the values with the budget deficit, which appears as the vertical black reference line.
In the bar graph, I stuck with the colors that McCandless chose to make it easy to compare his chart with mine, except that I tweaked a few colors a bit to resolve minor problems. In McCandless’ chart, some colors stand out more than others, but they should be equal in salience unless there’s a reason to feature some items over others. Also, for some unknown reason McCandless sometimes altered a single color from rectangle to rectangle, which serves no purposes and creates potential confusion. For example, notice that some of the green rectangles are lighter than others, yet they all represent “Earning.”
I can’t imagine anyone seriously arguing that McCandless’ chart communicates this information as well as the alternative above, but is his chart more engaging? Some folks might find it more engaging purely on the level of entertainment, but not in a way that encourages or supports meaningful consideration of the information, resulting in optimal understanding. Journalism should tell the story truthfully and clearly.