• Intra-industry trade and differentiated products emerged as a core explanation for modern trade, emphasizing simultaneous production, export, and import of close substitutes and the role of product differentiation in shaping trade patterns [11], [19], [6], [13].

• Tariff reductions, non-tariff barriers, and liberalization strategies are central to the evolution of trade regimes, illustrating how policy architecture shapes trade flows and welfare [5], [20], [2], [18].

• Gains from trade and elasticity analyses quantify welfare benefits and price responsiveness, guiding policy through estimates of overall efficiency gains and trade-induced price effects [15], [8], [16].

• Technology, R&D, and factor endowments are determinants of trade patterns, integrating technical change with endowment theories and examining capital mobility in trade dynamics [12], [7], [17].