This paper examines the impact of imperfect competition and international trade, focusing on fourteen industrial countries. The author, Elhanan Helpman, uses models of monopolistic competition in differentiated products to derive hypotheses about the volume and composition of trade. These hypotheses are tested empirically using cross-country comparisons and time-series data. The results suggest that larger volumes of trade are associated with greater differences in factor composition, while relative country size has a less significant effect. The paper also explores the share of intra-industry trade, finding that it is higher for countries with similar incomes per capita and decreases over time as differences in factor composition diminish. The findings support the theoretical predictions and provide insights into the dynamics of international trade.This paper examines the impact of imperfect competition and international trade, focusing on fourteen industrial countries. The author, Elhanan Helpman, uses models of monopolistic competition in differentiated products to derive hypotheses about the volume and composition of trade. These hypotheses are tested empirically using cross-country comparisons and time-series data. The results suggest that larger volumes of trade are associated with greater differences in factor composition, while relative country size has a less significant effect. The paper also explores the share of intra-industry trade, finding that it is higher for countries with similar incomes per capita and decreases over time as differences in factor composition diminish. The findings support the theoretical predictions and provide insights into the dynamics of international trade.