A Balls-and-Bins Model of Trade: Comment
指出Armenter和Koren模型假设出口货运规模与公司规模无关，但数据反驳了这一假设；使用实际货运规模后，模型无法再现单一产品/单一国家出口商的数据，说明货运规模是经济决策，不能作为纯统计基准模型。
We show that the Armenter and Koren model's firm-product-country results rely on the assumption that export shipment size is independent of firm size, and this assumption is contradicted by the data. When actual shipment sizes are used in the balls-and-bins model, it cannot reproduce the data on single product/single country exporters. Beyond just showing that the shipment size assumption matters to balls-and-bins outcomes, our results highlight the important fact that shipment size is an economic decision, co-determined with other export choices. For this reason, we argue that a balls-and-bins model cannot be a purely statistical benchmark model.