In Macroeconomics, it's often very hard, because once you've understood something, the various actors can adapt to the new knowledge, and then you have a new an

In Macroeconomics, it's often very hard, because once you've understood something, the various actors can adapt to the new knowledge, and then you have a new and different world economy. That is, if you publish your findings. I assume there are unpublished insights people use to get rich off. I think Friedman's analysis was mostly historical. At least that what I got from reading his book. I've certainly not read any academic papers. In Microeconomics, people can and do prove things based on models that are quite good at approximating reality.