When are tariff cuts not enough? Heterogeneous effects of trade preferences for the least developed countries
研究了OECD国家对最不发达国家的贸易优惠改革，发现关税削减促进了贸易流量的增加，但新贸易更可能出现在已有出口经验的产品或市场，未能实现广泛的出口多样化。
Poor countries export a remarkably narrow range of products. To what extent have trade preferences targeted to the least developed countries (LDCs) changed this situation? We study a large set of recent reforms to the LDC trade preferences offered by OECD countries. Leveraging trade policy variation by importer, exporter, product and year, we show that tariff reductions have increased the prevalence of positive trade flows. However, new flows have been far more likely to emerge in cases with previous 'export experience', i.e. where countries already exported the same product to another OECD country, or exported a related product to the same importer. So this wave of tariff cuts for LDCs has resulted in an extension of existing patterns of trade rather than wider export diversification.