The previous chapter has led us to investigate in depth, from the complementary viewpoints of optimization and reform, the normative properties of our model. At the present stage we should however consider two opposite drawbacks of our study: on the one hand, we have assumed too many degrees of freedom for the planner's action; on the other hand we have assumed too few such degrees of freedom for the same planner's action.

We have assumed too many degrees of freedom. This objection can be seen as an objection which is external to our approach: our assumptions on the degrees of freedom of the planner's action are grounded in more basic informational and observational assumptions and, if correct, the objection should concern these more basic assumptions. Indeed, the assumption that all transactions between the production sector and the consumption sector can be observed at no cost is an extreme idealization of the conditions under which the taxation power of the government can be exercised. In fact, the complete disconnection between consumption and production prices, permitted by the no-cost assumption, is not accessible to actual tax systems. Administrative costs - or what are usually considered as such - lead to a definition of a small number of categories of commodities, which are treated similarly - in the sense of being (usually) taxed at the same ad valorem rate. On the grounds of realism, a further step to our analysis would be to take into account these additional constraints. Note also that the above objection makes sense even as an objection internal to our approach.