A few thoughts about gauge charts

Gauge charts

A few days ago, I had a discussion about gauge charts. A colleague and I had reviewed a collection of operational dashboards. Some of them contained large sets of gauge charts. Those dashboards were the most ineffective. At the risk of repeating myself, here are some thoughts about gauge charts.

  • Gauge charts are not necessarily very effective at communicating information. Other chart types such as bar or bullet graphs are usually easier to read.
  • Gauge charts waste a lot of space. Dashboards should not require a user to scroll through its content. That would require them to use more working memory than we have. We therefore need to utilize the limited space we have in the most effective manner. Given the fact the gauges are not superior to other charts, why waste so much space.

Take a look at this example. Three of those bar charts fit into the space that is occupied by the gauge. Is the gauge more effective than the bar? I don’t think so. (By the way, the yellow lines indicate the range of the value.)

gauge chart
Two charts. Both convey the same information. Which one do you prefer?

Why then?

Most analytics professionals would probably agree with me that gauges are not that great. But why do we see them in so many dashboards then? I think the answer is pretty simple: People want to see them! The general level of knowledge about data visualization is still relatively low. Managers are therefore inclined to pick the chart types that look cool. Unfortunately, too many analytics professionals still shy away from pushing back on those requirements or they also lack knowledge. The lack of knowledge is also responsible that most software vendors feature gauges in their marketing materials (customers are asking for them).


It’s up to us analytics professionals to educate business users about gauge charts. Let’s start that process today! Also, look at your dashboards. Where do you have the ability to clean them up?


A Cognos 10 Dashboard

Cognos 10 offers a huge library of charts. Several new types were added in the last release. There are now over 160 different charts available. Amongst the new additions, you will also find Stephen Few’s bullet charts. They nicely complement the existing sparklines that were already available in version 8.4. Cognos 10 also provides new and enhanced color palettes that help design beautiful reporting objects. Overall, Cognos 10 offers some really cool options for building effective dashboards.


My colleague and friend Paul sat down last week to quickly create a sample dashboard in Cognos 10 using the new stuff. He took the new charts and also applied one of the palettes. Take a look – I love it! It’s simple but very effective. As a sales executive, I will immediately obtain an overview of my business.

Cognos Sales Dashboard


Bullet charts and sparklines are also available for Active Reports. You can therefore build awesome looking dashboards for online and offline use. Even better: they also work with the new iPad app.

If you happen to attend BAForum in Las Vegas in a few weeks from now, make sure to look for some the sessions that discuss Cognos 10 and dashboarding techniques in detail.



Hands-up! Here comes a bullet chart

Executives often want to have a quick overview of some key metrics to find out what the state of their business is. Questions like: Are my margins on target? Is customer satisfaction within an acceptable range? What is the size of my pipeline? All this information is typically summarized in a dashboard. The easy thing is to simply put this into a table. But tables are hard to read. And they take up a lot of space. The other popular option is to put the data into a gauge chart. But gauge charts take up a lot of space, too. And if we are honest with ourselves: they are really hard to read. Granted they look cool. But do they tell a story in an effective and efficient manner? Probably not.


A few years ago, Stephen Few introduced a new chart that promises to fix the shortcomings of the above described approaches. It is very simple but powerful chart and it is called ‘Bullet Chart’. Cognos 10 allows us to leverage these charts. Below is an example:

Let’s take a look. The above example shows the election results of a fictitious political party. The blue bar in the middle indicates the actual value (4.8%). The short black bullet towards the top indicates a target measure (e.g. budget, forecast, etc.). Color shades display ranges of performance (e.g. poor, acceptable, good). We can quickly see that the party missed the target but the result falls into the acceptable range. It is indeed a very simple chart that provides a lot of information in a concise manner: Target, Actual, Performance Rating. In Cognos 10, you have the ability to set five different performance zones in different shades or colors.


One the things I like about the bullet charts is the fact that you can easily stack them. That makes the bullet chart an ideal way of communicating multiple measures in a dashboard. It is easy to get a quick overview and the stack is very space efficient. In Cognos 10, we can have vertical or horizontal bullet charts.

The stack of bullet consumes little space


The are just two minor downsides that I see with the bullet charts. The chart in its pure form does not allow us to show the future trend or forecast. Also,  it does not display history. It is a simple snapshot in time. But the last shortcoming can easily be mitigated by combining the bullet chart with a sparkline. (I will look at sparklines in the next post)

Toss those gauges! Take a look at the bullet charts next time you design a dashboard. But make sure to train your users. Despite its simplicity, I have seen some people struggle to understand this chart. We don’t want our users to bite another bullet, right?