I would like to improve the readability of the label on charts.

At the moment there look like this 

![mockup](https://i.stack.imgur.com/cf2ND.png)

[download bmml source](/plugins/mockups/download?image=http%3a%2f%2fi.stack.imgur.com%2fcf2ND.png) – Wireframes created with [Balsamiq Mockups](http://www.balsamiq.com/products/mockups)

What is the best placement and orientation for chart label that offers a good readability and avoids wasting too much space ?