Several of the unbalanced growth theorists drew on Francois Perroux’s (1955) notion of “growth poles,” referring to investments in propulsive industries (the pole) in strategically located centers that induce growth by firms in technologically related industries through the formation of backward and forward linkages with the propulsive industries. Perroux saw growth in an economy as stemming from the effects of disequilibrium and domination, and necessarily occurring unevenly. To quote Perroux (1955: 309): “Growth does not appear everywhere at the same time; it appears at points or poles of growth with varying intensity; it spreads along various channels and with differing overall effects on the whole economy.” The growth pole was described primarily in terms of a complex of industries, using one another’s inputs and outputs (for example, the steel and machinery industries) and dominated by a propulsive or stimulant industry, the engine of development by virtue of its capacity to innovate and to stimulate, as well as to dominate, other industries (Parr 1999). This led to an interest in geography and regional planning between 1965 and 1975 in the deliberate formation of propulsive growth centers in poor regions. The growth-pole strategy typically focused investment at a limited number of locations (usually as part of a deliberate effort to modify a regional spatial structure) in an attempt to encourage economic activity and thereby raise levels of income and welfare within a region (for example, Semple, Gauthier, and Youngman 1972). Economic geography also had an interest in cumulative causation as a process that caused uneven development in space. Here the leading work by Allan Pred asked: Why do some cities grow more rapidly than, and at the expense of, other cities? Of several causes, Pred thought, initial advantage was probably most important. By initial advantage he meant processes like inertia and the temporal compounding of advantages and that, once concentration is initiated, it is self-perpetuating. The clustering of economic activity at selected locations created an agglomerative effect (firms get benefits when locating near one another), attracting new economic activity by serving as either national or regional centers for information accumulation or dissemination. Innovations made in cities have a neighborhood effect due to “distance decay” (that is, they affect nearby areas more), and so some places are more innovative than others. The more important the innovative center, the more rapid the economic growth. As the process evolved, a hierarchical structure emerged among the various urban places, essentially linked by the constant interchange of information (Pred 1965, 1973).