What was the main prediction of Malthus’ Essay on the Principle of Population? Did it come true? Is his essay still relevant today? How quickly did the global population grow during the twentieth century? What is the current global population growth rate? How is it changing? What is the neo-Malthusian perspective on environmental issues? How is future population growth going to be distributed across different regions of the world? Why is population momentum an important concept? What does the shape of a population age profile tell us about present and future population growth? What is the demographic transition theory? What happens to birth rates, death rates, and population at each stage? According to economic theory, what is the relationship between population growth and economic growth? How can rapid population growth undermine economic growth? What is IPAT and what is its relevance for considering the future of the environment?