Macromodelling as an exercise

Here's a small exercise in macromodelling which helps with understanding how the economy works. The exercise involves modelling mathematically a simple economy in full, capturing all essential aspects of the macroeconomy - the interaction between money, saving, and the goods market, as well as debt, price determination, international trade, and so on. The modelling should be microfounded, so that the decisions of individual people and companies in the economy should be considered in determining aggregate behaviour. The economy should have enough people, companies, and other actors in it to allow for all of the aspects of the economy, but no more.

The exercise offers benefits in that one comes away from it with better understanding of the macroeconomy, and more knowledge of the contents and limitations of other people's models. I set the exercise's time limit for myself of a couple of hours, so I always (so far) fail to model adequately, but the benefits still accrue.