I recently ran across this paper in *Food Policy* published back in 2011 by Charles Nicholson, Miguel Gomez, and Oliver Gao. The paper asks an interesting question: what would happen if we required food (or in this case, milk in particular) to be more local? This is a policy proposal that has been seriously put forth by prominent food writers.

The authors took data on current location of milk production, processing plants, and consumers and created a mathematical model to minimize the cost of supplying various dairy products to consumers. Here's their description of the spatial dimensions of the data:

Given this set-up, what is the effect of cost of reducing the number of miles traveled - or the weighted average source distance (WASD) - by 10% or 20%?

The authors find that (in the month of May), requiring a 10% or 20% reduction in WASD would increase total costs by about $1 million and $18 million per month (0.1% and 1.7% cost increases), respectively. All this is a way of saying that milk production and dairy processing is located in particular regions for a reason, and forcing a different spatial configuration will increase costs. The authors write:

In other words: the effects are complicated and impose much larger costs on some portions of the supply chain than others. In terms of the impacts on consumers:

Another interesting result is that even though WASD is reduced over all by 10% or 20%, some dairy products, such as cheese, end up having to be transported even further.

The authors consider another interesting scenario in which people just want to reduce the distance traveled by fluid milk by 10%. In this case, total costs increase a whopping 12%, and the WASD for all products actually *increases* by 98 miles (a 31% increase in distance traveled). This remarkable result shows the unintended result of, for example, local schools requiring their milk be purchased locally without considering what happens to the yogurt, butter, cheese, and nonfat dry milk that will also be consumed by someone.

The authors conclude as follows: