This introductory chapter focuses on the concept of development. The low standard of living of the mass of the population in developing countries is singled out as a key issue in development. The development of per capita income over time and the factors that influence economic development or stagnation are important topics in the book. However, the interplay between economic and non-economic factors is also of great importance for our understanding of the dynamics of socio-economic development. Economic growth can not be explained by economic factors only, and the concept of development includes more than mere changes in economic indicators.