Implicit in structural-change theories and explicit in international-dependence theories is the notion of a world of
dual societies, of rich nations and poor nations and, in the developing countries, pockets of wealth within broad
areas of poverty. Dualism is a concept widely discussed in development economics. It represents the existence
and persistence of increasing divergences between rich and poor nations and rich and poor peoples on various
levels. Specifically, the concept of dualism embraces four key elements:viii
1. Different sets of conditions, of which some are "superior" and others "inferior," can coexist in a given space.
Examples of this element of dualism include Lewis's notion of the coexistence of modem and traditional
methods of production in urban and rural sectors; the coexistence of wealthy, highly educated elites with
masses of illiterate poor people; and the dependence