Problem: Poor line work near center of pie chart symbology in ArcMap
The outlines of pie chart slices overshoot the center of the chart during symbolization.
Cartographic Line Symbols has a limitation where it bends at a very small angle. This happens at the center of the pie for very small slices and the problem is magnified if the line width is increased.
Solution or Workaround
The following solution involves changing the line symbol used for the pie chart slice outlines.
Here is an example of the wedge line work for a pie chart which needs improvement.
Open the Layer Properties dialog box for the layer and select the Symbology tab.
Click Symbol and choose Properties for All Symbols.
In the Symbol Property Editor dialog box, change the wedge outline symbology using one of these options:
A) Click the Type dropdown list and select Simple Line Symbol rather than a Cartographic Line Symbol.
B) Use the Cartographic Line Symbol and change the Line Joins setting to use the 'Round' option.
Click OK to all of the dialog boxes to apply the symbology change.
After implementing one of these changes, the pie chart line work will be of much better quality.