One way to create borders is to do a dual axis so the second axis is a line, not a polygon.
To do this;
- Drag out another instance of AVG(Latitude) onto the rows shelf
- A new series will appear in the marks card, change it's type from Polygon to Line.
- In the line series, remove the % of females from the color card and replace it with the 'name' field you're using.
In the attached example, I've also created a group on your 'Name' field to give you the border breakdowns you outlined in your first post and I took the transparency of the polygon colors up a bit so it was a bit easier to see the borders.
Thematic polygon maps_TW.twbx 63.8 KB