Recent theoretical developments have incorporated endogenous multinational firms into the general-equilibrium model of trade. One simple taxonomy separates the theory into vertical' models in which firms geographically separate activities by stages of production and horizontal' models of...

The comparative advantage of many cities is based on their efficiency in the production of 'functions', e.g., business services such as finance, law, engineering, or similar functions that are used by firms in a wide range of sectors. Firms that use these functions may choose to source them...