Why do health disparities exist?

I found a graphic created by the Center for Health Equity Research and Promotion Collaborations (CHERP) that captures at least 6 factors that explain why health disparities exist.

They are as follows:

1. Individual
2. Environmental
3. Social
4. Provider
5. System
6. Policy

Source: http://www.cherp.org/primer3.php

We need to expand upon charts like this to provide as much detail and clarity as possible. I welcome your comments and ideas!