An important aspect of these criticisms is the nature of the model used by the TPC to model tax changes, which assumes away any major impact on labor supply, capital formation or economic growth from reform. The critics argue such 'static' models (including those used by the US Treasury Department and Joint Committee on Taxation) are only suitable for modelling minor incremental changes to the system (see citations below).

The excerpt from a paper by Harvey Rosen of Princeton University cited below provides the most detailed statement of this objection of the studies that have been mentioned in the debate.

For the objection to hold water the posited macro-dynamic effects would need to be significant. Several attempts have been made to put some numbers on this and to show they make the Romney plan viable. These, along with objections to them, are mapped in the sub-structure to this node. The TPC's defenses against this criticism are also included.