19th centuries down to the ecological concerns that emerged in the second half of the 20th century and developed into the formation of ecological economics as an independent academic subdiscipline in economics. Concept of the stationary state in classical economics From Adam Smith and onwards, economists in the classical period of economic theorising described the general development of society in terms of a contrast between the scarcity of arable agricultural land on the one hand, and the growth of population and capital on the other hand. The incomes from gross production were distributed as rents, profits and wages among landowners, capitalists and labourers respectively, and these three classes were incessantly engaged in the struggle for increasing their own share. The accumulation of capital (net investments) would sooner or later come to an end as the rate of profit fell to a minimum or to nil. At that point, the economy would settle in a final stationary state with a constant population size and a constant stock of capital. Adam Smith's concept Adam Smith's magnum opus on The Wealth of Nations, published in 1776, laid the foundation of classical economics in Britain. Smith thereby disseminated and established a concept that has since been a cornerstone in economics throughout most of the world: In a liberal capitalist society, provided with a stable institutional and legal framework, an 'invisible hand' will ensure that the enlightened self-interest of all members of society will contribute to the growth and prosperity of society as a whole, thereby leading to an 'obvious and simple system of natural liberty'. Smith was convinced of the beneficial effect of the enlightened self-interest on the wealth of nations; but he was less certain this wealth would grow forever. Smith observed that any country in the world found itself in either a 'progressive', a 'stationary', or a 'declining' state: Although England was wealthier than its North American colonies, wages were higher in the latter place as wealth in North America was growing faster than in England; hence, North America was in the 'cheerful and hearty' progressive state. In China, on the other hand, wages were low, the condition of poor people was scantier than in any nation in Europe, and more marriages were contracted here because the 'horrid' killing of newborn babies was permitted and even widely practised; hence, China was in the 'dull' stationary state, although it did not yet seem