At the opposite end of the ideological continuum are a set of struc- tural theories that view migration flows as a reflection of the ever-grow- ing articulation of the global capitalist economy and its changing labor needs. From this perspective the central difficulty with push-pull, economistic, and labor-recruitment theories is not that they fail to identify important forces but that they do not take into account the changing historical context in which they operate. For each of these theories migra- tion occurs between two distinct, autonomous social units: that which expels labor and that which receives it. The possibility that such flows may actually be internal to a broader system to which both units belong is not contemplated. An alternative conceptualization of the origins of migration requires a grasp of the character of this changing global system and of the mode of incorporation of different areas into it.