On the Principles of Political Economy and Taxation (19 April 1817) is a book by David Ricardo on economics. The book concludes that land rent grows as population increases. It also presents the theory of comparative advantage, the theory that free trade between two or more countries can be mutually beneficial, even when one country has an absolute advantage over the other countries in all areas of production.

David Ricardo's On the Principles of Political Economy and Taxation the implications of land rent increases along with population among other things. Ricardo argues for the acceptance of free trade and shows how it's both short and long term advantages. The arguments laid out in this book form the basis of modern trade theory and are, therefore, of interest in today's global economy.