One of the clearest correlations in development is that between quality of governance and wealth. You can see the relationship in the chart below (from this excellent but paywalled article in the Annual Review of Political Science).
Wealthier countries are better governed countries — this is clear. What is less clear is whether wealth causes good governance, or whether good governance causes wealth, or whether some third factor (maybe education, for example) causes both.
Read the rest of this post at the Devpolicy blog.