A new paper by Trevor Tombe in the American Economic Journal: Macroeconomics provides a cautionary tale for those who think we'd be better off economically if we sourced more food closer to home.
The paper starts off with this stylized fact
The problem, it seems, is that poor, agricultural-based countries don't trade.
These "trade costs" that are holding up trade include bad policies like tariffs but also bureaucratic problems like border delays.
The paper has a nice set graphs, and the following shows a few of them related specifically to agriculture.
First, when you don't trade agricultural products with you're neighbors, you tend to be poor.
Countries that have more agricultural trade have higher GDP/worker. The correlation is 0.68. Countries that have more agricultural trading partners tend to be richer and more productive.
A lot of local food advocacy is premised on the idea that we need smaller farms with more farmers. I don't think anyone would argue that greater local food production would mean more employment in agriculture. Well, would that be good for the economy? According to this paper, no. This graph shows a very clear negative correlation between a country's employment share in agriculture and GDP/worker. More workers in agriculture is typically going to mean lower economic output.
Finally, this graph shows that the higher the share of food spending on domestic output (i.e., the more local foods purchased), the lower the country's GDP/worker.
There's no reason to believe what's true of countries wouldn't also be true for states or cities trading with each other.
The author concludes: