AC: Gauges are used more often than they should be. Why do you think people are so enamored with these inefficient visualizations?

SF: This interest in gauges exists partly for the reason described above: the appetite for silly gauges is stimulated by ubiquitous examples. There's more to than this, however.

First, people love metaphors. Dashboard vendors didn't begin developing gauges that look like automobile dashboards because they work well for computer-based performance monitoring displays. They did it because they took the dashboard metaphor too far. The metaphor is only useful because of a conceptual similarity between automobile dashboards, which are used to quickly monitor what you need to know when driving a car, and computer-based information dashboards, which are used to monitor some aspect of the organization. Beyond this similarity, the metaphor is both useless and dangerous. What works for driving a car is not what works best for doing your job. Most vendors never bothered to question this. Instead, they just followed the herd. Rather than developing products that work effectively, they spent their time coming up with more and flashier gauges.

Second, gauges are cute and fun. They have needles that bounce back and forth, they have light and shadow effects that make them look like the sun is shining on them, and they have bright colors that shout, "Look at me." Are our organizations well managed by playing with things that are cute and fun? Don't get me wrong, I like cute and fun as much as the next guy, but I chose my wife for reasons that go beyond this--she provides what I need in a partner. We should choose dashboards that give us what we really need. Dashboards should always display data as clearly, accurately, meaningfully, usefully, and efficiently as possible. I've seen few gauges that do this. Most of them use up a great deal of space to say very little, and what they do say they say poorly.

AC: So it sounds like there are gauges that effectively communicate data, albeit a rarity. Do you have an example?

SF: The purpose of a gauge is to display a single measure of something that's currently going on. To do so effectively, it also includes context in the form of one or more comparisons (for example, compared to a target or the same measure at some point in the past, such as on this day last year). Also typical of gauges is a visual indication of qualitative state, which is usually handled using traffic light colors (red for poor, etc.). These attributes describe what gauges attempt to do.

Because dashboards must display a great deal of information in a limited amount of space (that is, a single screen), all forms of display, including gauges, must use space efficiently. Circular gauges, by their very nature, waste space, so I've never seen a circular gauge that works well on a dashboard. This leaves us with gauges that are linear in design. Of the linear gauges that I've seen, few display a measure of what's going on with sufficient context or provide a visual indication of the performance state that is rich in information, efficient in its use of space, and designed for quick and easy comprehension. This is because few were actually designed by people who understand the best practices of data visualization that have developed from research into visual perception and cognition. One exception is the gauge that I invented a few years ago called a "bullet graph."