Simon Rogers has created a visualisation showing death penalty statistics, country by country, for the Guardian Data Blog.
The visualisation uses a bubble graph on a map of the world to depict how many people have been given death sentences and how many people have been executed in 2011. This is then broken down by country, giving users the opportunity to compare and contrast regions.
Death sentences are presented using orange bubbles and executions using red. This simultaneously gives the user two sets of data in a comprehensible way. It is also possible to compare and contrast the number of sentences with the number of executions in each country and to see how countries differ from each other in this. For example, the USA handed out 78 death sentences and executed 43 people, whereas Nigeria handed out 72 death sentences but no one was executed in 2011.
The colours chosen, red and orange, are distinct enough for the visualisation to be clear. However they are similar enough to reflect the fact that they are presenting similar data. Red also connotates death, a symbolism users will be familiar with. The colour scheme thus contains information in itself and makes the visualisation comprehensible.
The bubbles have been made on a scale to show a large variation in size. There is thus a clear difference between the size of Ghana’s bubble, which shows that only four people have been sentenced to death, and China’s , which demonstrates that ‘thousands’ have been killed. The eye is automatically drawn to the larger, bright red bubbles of China and Iran, and thus the most shocking and important information is highlighted to the user.
The number of sentences and executions and the name of each country are written inside the bubbles. Additional information is written outside the bubbles with arrows pointing to them, for example that ‘Iran, along with North Korea, Saudi Arabia and Somalia carried out public executions in 2011.’
To give an overview the visualisation uses text to say that ‘676 executions were known to have been carried out in 20 countries in 2011 and 1,923 people in 63 countries were known to have been sentenced to death.’ It also tells us that this does not take into account the unknown numbers of people executed in China.
A bar chart is used to document the number of countries that have carried out executions from 1991 to 2011. This information could be gathered from the bubble chart for 2011 but by putting it into a bar chart the user can see it easily and instantly. The number can also be compared with other years and the general trend is that the number of countries carrying out executions is going down.
The visualisation is a sophisticated way of showing a large amount of information and making it comprehensible. It highlights the most important information and allows the user to compare and contrast, giving them the ‘big picture’ of differences between countries over a series of years. It did, however, leave me wondering why there was a large disparity between the number of people sentenced and the number of executions taking place.