期刊
EUROPEAN REVIEW OF AGRICULTURAL ECONOMICS
卷 40, 期 2, 页码 331-360出版社
OXFORD UNIV PRESS
DOI: 10.1093/erae/jbs028
关键词
gravity model; selection bias; agrifood trade; Heckman selection model; marginal effects; F10; F12; F19; Q17; R12
资金
- Ontario Ministry of Food, Agriculture and Rural Affairs
- Canadian Agricultural Trade Policy and Competitiveness Research Network
- Agriculture and Agri-Food Canada
In the analysis of bilateral trade flows, reported trade of zero or missing observations is quite common and this is a problem when estimating log-linear gravity equations. This has caused many researchers to either ignore the zero trade flows or replace the zero with a small positive number. Both of these actions bias the resulting parameter estimates of the gravity equation. In this study, we correct for this misspecification by using the Heckman selection model to estimate bilateral trade flows for 46 agrifood products, for the period 19902000, for 52 countries. In our sample, selection bias rarely affects the signs of variables but often has a substantial effect on the magnitude, statistical significance and economic interpretation of the marginal effects. Hence, treating zero trade flows properly is important from both a statistical and an economics perspective.
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