The Global Spread of Liberty and Democracy: A Brief Discussion is a short paper looking at the evidence regarding the level and change in access to liberties and democratic systems worldwide. It briefly discusses the history of the ideas of liberties and rights, long-term evidence regarding their extent, and two centuries of evidence regarding their spread as measured by the Polity dataset. In particular it looks at potential causes for the spread of liberties and democracy over that time period and suggests an important role for changes in the demand for such liberties which is weakly related to income change.