Keep the pie for birthdays

Today's Kuensel's front page article reported the 2010 land cover assessment statistics. These statistics are important: according to the Kuensel article, they are "used for planning and monitoring of land based resources by agencies like the GNHC and NSB".

Charts are excellent for communicating such statistics. However, creating effective graphs is not simple. The Kuensel chart showing the land coverage by type of land looks like this:

Chart from Kuensel newspaper, June 8, 2011

What exactly can we learn from this graph? Clearly there is one big blue slice that with some effort we can map to "Forest". But what about the others? Try taking this quiz:

1. What is the green slice? (you have 3 seconds)
2. Can you quickly compare Meadows with Snow Cover?
3. What do the numbers mean?
4. What is the third largest type of land?
5. What is the smallest type of land?

Let's see a more effective plot using the same data (and the same software -- I am using Microsoft Excel, the same software used to produce the Kuensel graph):

A more effective chart of the same data (using the same software)

Now try that quiz again! Of course, there is no green slice anymore. We can easily see how "Forest" is by far the largest, we can also easily see that "Snow cover" is the third largest. And Non-built up areas is the smallest. We can also more easily compare the different types of land to each other.

Here are a few guidelines for creating an effective plot for percentages:

1. Avoid pie charts! They are known to be ineffective communicators. Bar charts almost always convey the information in a clearer and less misleading way
2. Include informative labels: the Kuensel chart does not have any title, no % sign (maybe those numbers convey squared km?)
3. Avoid 3D charts -- in this case the third dimension is only confusing.

Creating effective charts is an important skill, especially in journalism. Charts should be effective, not "artistic".

Here's a cool site by Stephen Few that shows examples of poor charts. Click on each to see a quick analysis and an example of a good chart for the same data. An excellent book by the same person is Show me the Numbers. You can view part of the book using Amazon's Look Inside, and you are welcome to come and browse my copy.

A final challenge: can you create a better chart for each of the two charts from today's article "Cash in banks come from corporations" shown below? (hint: use the 3 tips and think "effective", not "artistic").

How to convey the information from this pie chart more effectively?

How to improve this bar chart so that readers more easily grasp the story?