Spatial perception: on the chart and in real life
Pi Day Special: #onelesspie initiative to clean up Wikipedia

Setting the right priority

On the sister blog, I wrote about a new report on the music industry lamenting that the hype over "Long Tail" retail has not really helped small artists (as a group). This was a tip sent by reader Patrick S. He was rightfully unhappy about the chart that was included in this summary of the report.

Superstar-music

This classic Excel chart has some basic construction issues:

  • The data labels are excessive
  • The number of ticks on the vertical axis should be halved, given the choice to not show decimal places
  • With only two colors, it is a big ask for readers to shift their sight to the legend on top to understand what the blue and gray signify. Just include the legend text into the existing text annotation!

In terms of the Trifecta checkup, the biggest problem is the misalignment between the intended message and the chart's message. If you read the report, you'd learn that one of their key findings is that the top 1% (superstar) artists continue to earn ~75 percent of total income and this distribution has not changed noticeably despite the Long Tail phenonmenon.

But what is the chart's message? The first and most easily read trend is the fall in total income in the last 12-13 years. And it's a drastic drop of about $1 billion, almost 25 percent. Everything else is hard to compute on this stacked column chart. For example, the decline in the gray parts is even more drastic than the decline in the blue.

It also is challenging to estimate the proportions from these absolute amounts. Recognizing this, the designer added the proportions as text. But only for the most recent year.

So we have identifed two interesting stories, one about the decline in total income and the other about the unending dominance of the 1 percent. This is where the designer has to set priorities. Given that the latter message is the headline of the report, it is better to plot the proportions directly, while hiding the story about total income. The published chart has the priority reversed. Even though you can find both messages on the same chart, it is still not a good idea to highlight your lesser message.

 

Comments

craig w

Another missing (and maybe misleading) element is the number of artists represented each year. It seems quite possible that the number of artists in 2013 is much larger than 2000.

So while it's true the 1% dominance is growing/maintaining, the dominance of the top 50 artists may be shrinking if the overall pool of artists is increasing.

In other words, 1% of the artists may not accurately represent "superstars". In fact the article mentions 25M digital tracks with 1% representing 250,000 tracks. Clearly those are not all written by what anyone would consider superstars.

Perhaps a better measure would have been a fixed number of artists?

daniel l

I use something like this on a regular basis: scenario is a percentage based kpi where I have winners and losers. I use a line/stacked bar combo with my winners in a muted series, losers as a highlighted series, and the KPI itself as the line.

I always felt like it passes the trifecta in that: the chart answers any practical question one might have with a high degree of self sufficiency. Any question you'd have about the number 95%: how many actual losers, how many total is answered, and what's the percentage is being answered.


But now hearing Kaiser take this apart, my friday is ruined!!!! :)

Andrew Gelman

Kaiser:

I'd like to recommend another option: display 2 graphs, one showing the trend of the total, the other showing the trend in the proportions. No need to cram all the information into one graph.

Kaiser

Andrew: Good point. If both messages are important, we should use two charts. For business metrics, I have always found it necessary to produce two almost identical sets of charts, the only difference being absolute and relative metrics so one version shows the trend in number of sales and the other one shows the trend in sales rate.

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