This book is a collection of published articles written by Professor Ronald Jones in the field of international trade theory. The focus of this publication is the use over time of simple models. Several of the classic questions of competitive international trade theory are raised throughout. What explains the pattern of a country's trade with other countries? In particular, if prices change for commodities that are traded in world markets, what are the consequences of such changes on markets that are purely national, and not global? Alternatively, when a country's factor endowments change, what are the consequences for that country's production patterns for goods traded in a world markets? If production technologies improve, what are the consequences for commodity prices and factor returns? In answering these questions, it becomes clear how the models differ from one another, and how, with growth in trade, the selection of models changes. Which model is most appropriate depends on the nature of the changes of economic growth. International trade is best understood through the use of a variety of these simple trade models.