Chapter 26 International trade theory: The evidence This chapter focuses on the international trade theory. It discusses the Ricardian and the RicardoViner models. These models point to technological differences as the source of international comparative advantage. A simple Ricardian model has one input labor which is assumed to be mobile across the two sectors of the economy but internationally immobile. The RicardoViner model introduces into the model two additional factors that are sector specific. This gives curvature to the production possibilities curve and also allows international commerce to affect the distribution of income. Although there is little or no direct empirical support for these simple models there is nonetheless growing awareness that technological differences are a natural consequence of economic isolation and play a role in the integration process following an economic liberalization. The chapter provides an overview of the HeckscherOhlin model and discusses the Rybcyzinski theorem and the StolperSamuelson theorem. It also reviews the studies of the HeckscherOhlin model based on cross country comparisons.