Recently, I’ve taken part in a discussion about how to present numbers to convey a message about true people stories.
We often forget that these are not only numbers. Each number represents a human being, his/her tragedy and tragedy of her/his relatives.
Statistics often show numbers, % of populations, rises, falls and trends. There is a huge challenge and effort to depict context and tell the story behind datasets. Especially, when we try to depict in numbers the phenomenon such as #COVID-19. We have to remember that “confirmed cases” are real people, who are diagnosed with coronavirus. A number of deaths is a number of people who lost their lives because of this disease.
Daily, we are exposed to numerous statistics in media, workplaces, schools. They describe current situations, accidents, local and global events like car accidents, infants mortality or unemployment. Most of them are expressed as a ratio or percentage. These formats are not intuitive and for most people are hard to interpret. However, there are some methods, which connect numbers with people.Maybe not with individuals, but with countable human beings, with whom we can empathize.
A good example is the unemployment rate, which is one of the most important economic indicators. In the governmental statistics, unemployment is presented as a ratio of employees to all people who can work.
An unemployment rate expressed as a percentage does not cause any emotions among most of us. Most of us understand what see, but … it is nothing personal. Percentages are abstract objects. It is about closer indefinite part of the population throughout the country.
As studies show, we can transform this message in a way to evoke people feelings and make them start to take a more human perspective. Instead of abstract 20%, we can present that 1 out of 5 people is unemployed. Each of us can count to five. Each of us can easily list five people. Behind this number, people’s faces may stand. In such a small group of people, our neighbour or our family member may be out of work. This is no longer an abstraction but a very real threat.
The one dataset, two charts, two opposite stories.
The introduced scale has a huge impact on how we digest and interpret the presented data. The linear scale represents natural numbers, which we can easily compare. The logarithmic scale is not intuitive for us. It’s a mathematical concept, which we can use when we want to describe multiplicative factors or when is a huge skewness towards large numbers. We need to use brainpower to understand it. What is more, we are so used to linear one that we can easily overlook that visual is depicted on a logarithmic scale. We should inform our audience that logarithmic is used… and make sure that they understand how to read it.
Because of COVID-19 huge amount of statistic are generated and published across the internet. Those statistics try to tell a story about COVID-19 phenomenon. Most of them focus on a number of confirmed cases and deaths. I notice two data visualisation’s trends regarding presenting data about this virus. The first one concentrates on the growth of a total number of confirmed cases and the second one on the pace of disease spreading.
Let’s feel the difference.
“PANIC chart” — I saw somewhere a good name of such a linear chart. I couldn’t more agree. Tell me, what feelings this chart evokes in you?
This is an exponential chart (another mathematical concept), which depict the growth of the phenomenon. Very rapid growth to be specific.
Below we can see the same data. However, embedded on a different scale. Please, look carefully. Each grid represents 10 to n power. Don’t you think that the below chart isn’t so scary?
What stories these two charts tell us?
Let’s base them on 18th of Mar and 4th of Apr. The Linear chart tells us that till 18th of Mar nothing spectacular happened. Totally opposite to the Logarithmic one, where we can see the fastest growth of confirmed cases. Between 18th and 4th on the Linear, we can see the huge growth. On the second one, the pace of growth decelerates. After 4th of April, the Linear continues to present the same pace of growth (steep hill), but on the Logarithmic, it’s plain to see that the curve flattens.
Recently, I have had an interesting discussion about the pie charts. My interlocutor claimed that the pie charts should be in usage because they are intuitive, and people decoding information from them very quickly. Well, it’s exactly opposite, how research shows. The human brain cannot quickly and accurately compare several angles. What is more, on the pie chart there are not only angles but areas and colours which confuse the human brain as well. As proof, check out the paper of W. Cleveland & R. McGill about the visual decoding of quantitative information. So, how to cope with part-to-whole cases? What instead of the pie charts? How to effectively convey information?
Paulina, what is wrong with you? Why do you hate those pie charts so much? Look. They are based on the ideal shape, and you can use all your most favour colours at once!
Unfortunately, those colours and this ideal shape are a true curse in the clear interpretation of the data. Research shows that the human brain has problems with decoding quantitive information presented by those three attributes:
Let’s see an example. Imagine that parts of the wheel are product categories which you offer in your store. You would like to find out which category is the most profitable one. What kind of question would you ask?
Which category sales the best? Which one is the worst?
Let’s see how visual decisions can affect the process and speed of getting valuable insights.
Note: I’m not adding data labels on purpose. I want to focus only on visual decoding (without text support).
I would never choose a pie chartto compare more than two categories. Are you able quickly and accurately answer questions statement in the example? I’m not. NOT AT ALL.
100 % STACKED BAR CHART
We can instead of pie chart use 100% stacked bar chart, up to some point. Research shows that people are quite good at comparing lengths. However, colours can distort lengths. The more saturated colours, the larger the object seems to be. The second issue is again with many categories. The more of them, the workload for comparing elements increase.
STACKED BAR CHART
This is my first choice. There is no field to mislead anybody with a stacked bar chart.
As I mentioned, people are quite good at comparing lengths. When we use one colour of bars, we can be 100% sure that no one will have issues to recognize the longest and the shortest bar. One blink of an eye and you understand what you see. For your lazy brain, it is pure magic.