The Gravity of Intermediate Goods

Review of Industrial Organization - One of the puzzles of the gravity literature is the persistent effect of distance on trade flows, despite the dramatic fall in trade costs during the last few...     

A Comparison of EPI Sampling, Probability Sampling, and Compact Segment Sampling Methods for Micro and Small Enterprises

Finding an efficient method for sampling micro- and small-enterprises (MSEs) for research and statistical reporting purposes is a challenge in developing countries, where registries of MSEs are often nonexistent or outdated. This lack of a sampling frame creates an obstacle in finding a representative sample of MSEs. This study uses computer simulations to draw samples from a census of businesses and non-businesses in the Tshwane Municipality of South Africa, using three different sampling methods: the traditional probability sampling method, the compact segment sampling method, and the World Health Organization's Expanded Programme on Immunization (EPI) sampling method. Three mechanisms by which the methods could differ are tested, the proximity selection of respondents, the at-home selection of respondents, and the use of inaccurate probability weights. The results highlight the importance of revisits and accurate probability weights, but the lesser effect of proximity selection on the samples' statistical properties.     

Pecking order and core‐periphery in international trade

This paper analyzes the impact of market size and trade costs on bilateral trade flows. A multi‐country trade model with firm‐level heterogeneity in productivities and countries’ market potential provides a simple micro foundation for the link between these variables. In the model, market size and trade costs jointly determine a country‐specific pecking order of exporters serving their destination countries. In a counterfactual setting where bilateral trade costs are homogeneous across country pairs, market size predicts a common ranking of exporters among destination countries. This leads to a unique core‐periphery structure of the world trade network. With heterogeneous trade costs, we illustrate the impact of market size and trade costs on bilateral trade flows and its margins in a simple gravity‐like setting. Using an instrumental variables approach, we find that both market size and trade costs (measured through the network position of countries) have a significant impact on bilateral exports: countries in the core bilaterally trade more with other countries in the core than with peripheral countries, conditional on typical observables.