I've been critical of many of the local foods policies that have been touted as solutions to economic, environment, or health problems (e.g., see here or here). Much of my criticism is rooted in the fact that advocates have failed to meaningfully and accurately articulate how policies to, say, require local schools or hospitals to source food within a certain radius or to subsidize farmers markets will improve the environment or increase a region's economic growth.
In the debate about local foods, proponents and opponents have largely talked past one another, and one of the hindrances to more fruitful dialog is the lack of a formal mathematical model from with people can illustrate the effects they believe to disseminate from promotion of local foods. While surely not everyone will agree with the details of any particular model and the conclusions coming from it, a model at least provides a starting-point from which one can articulate what they believe the model is missing which would justify or condemn local food policies.
Enter this new paper by Jason Winfree and Philip Watson in the American Journal of Agricultural Economics. The authors present just such a mathematical economic model in which one can talk about the benefits and costs of local food policies. They generally show that local food policies are more costly than beneficial. However, they do show that in certain conditions (if there is a lot of market power and extensive externalities), it is possible (though not necessarily likely), that local foods policies can produce more benefits than costs.
In a blog post at Oxford University Press discussing their paper, they summarize their findings as follows.