Pie and Doughnut series can be linked. This is most visible in Excel when you create a doughnut chart with a bunch of series; if you change the angle of first slice, all the series will rotate. This is because doughnut series, by default in Excel, are created in the same group (you can force it to have multiple groups by doing things like creating a line chart, and converting the series one-by-one to doughnut series). If you have multiple pie series in the same group, you only see one of them. This linking between series is maintained in the api, and noted on the individual properties. | 