It is impossible to overstate the importance of adding context to analysis. Take the example of having the headline number Average Call Time displayed on a dashboard. While this might clearly be an important metric for a call center, on its own it portrays very little.

As shown in the Dimensionless bar chart recipe, we use reference lines to add the context required to make the number meaningful. Sticking to the example of Average Call Time, we may also want to also see a previous point-in-time position, the national or a competitor's average, the internal target, and so on. This recipe extends the use of reference lines further.