Troubleshooting 100% Stacked Bar Chart
 

I have a 100% stacked bar chart that displays % of budget expended (Series A)
and % not expended (Series B). Most of the time, both series are
proportionally displayed in the graphic (e.g., 60% and 40%). However, when
Series A exceeds about 80%, the proportions on the graphic become distorted
(e.g., 88% expended appears to be about 40% of the total bar, the remaining
12% takes up about 60% of the total graph).

Any thoughts about how to resolve this?
Thanks.