These are theories related to economic development, often discussing factors that hinder or promote growth in developing economies. - Critical Minimum Effort Hypothesis was proposed by Harvey Leibenstein, suggesting that a developing economy needs to achieve a certain minimum level of investment to break free from the "low-level equilibrium trap". - The Theory of Social Dualism was put forward by J.H. Boeke, describing the coexistence of pre-capitalist (traditional) and capitalist (modern) social systems in developing countries. - The Low-level Equilibrium Trap is a concept discussed by several economists, prominently by Richard Nelson, where a country's per capita income remains low due to factors like high population growth offsetting gains from investment. - The Theory of Technological Dualism, often associated with Benjamin Higgins, refers to the coexistence of advanced, capital-intensive technology and traditional, labour-intensive technology within an economy.