Maps will typically display one data variable or indicator, often using colour coding to indicate the density, frequency, or percentage in a given region, allowing quick comparison between regions. Colour coding can also be used to show changes over time (e.g. red for regions where an indicator got worse between two specific years, blue for areas where an improvement was seen and so on). Other information can be overlaid on the map, for example specific sites (e.g. hospitals or distribution centers) and text.