Using Business Intelligence Dashboard Designer : Creating a New Dashboard : Working with the Chart Designer : Pie Charts
  

Pie Charts

If you are comparing parts of a whole, consider using a pie chart. Key words associated with charts include, portion, share, and percentage. If for example, you want to demonstrate the proportion of the company's budget spent on health insurance, use a pie chart. To make the chart easier to read limit the number of slices to five. Pie charts can also be exploded, which means certain slices are pulled away from the remainder of the chart for emphasis.
http://infocenter.pentaho.com/help/topic/puc_user_guide/images/12_exploded_pie.png