Brian, the monkeys sicken on the grazer, omnivore, and carnivore diets.

Patrick, I agree that a wide range of options is better than the current US system. At some point, however, that wide range of choice sabotages attempts to measure the effectis of schooling. Consider the conclusion to my post “What’s a Linear Differential Operator, Anyway?”. According to one of the chapters in Vouchers and the Provision of Social Services, standardized Math test performance is lower and standardized Lagguage test performance is higher in countries which subsidize parent control bud DO NOT require schools to assess students’ Math performance than in countries which subsidize parent control and DO require schools to assess Math performance. I infer that Math matters more to Education Department bureaucrats and to politicians than it does to parents.

I would also like to see the rigorous research that has been done on this zoo food issue. I had no idea that antelope can’t live on mangos and guavas, but apparently pigs can? But alfalfa kills pigs? And 3/4 of the monkeys die? Really? You would think mangos and guavas would be perfect for them.

As far as the analogy (Malcolm), these studies do let the “animals eat what they want.” Animals who are malnourished are identified. Some of these animals graze on whatever they normally eat, and some randomly have a bucket of mangoes or alfalfa offered to them. And then the animals eat whatever they want. Compliance is voluntary. I think you suggest that you think that selection bias is a good thing because you think some sort of voluntary choice needs to be a part of the analysis. Well, it is. The only thing that is randomly assigned are the amount of options the treatment and control groups have. What they do with those options is up to them. I think that good evaluations of choice are not (should not) be thought of as evaluations of alfalfa or mango diets, they should be thought of as evaluations of “choice.”