In this article the authors define sustainable development as an economic
programme along which social well-being does not decline over time. It can be
shown that the requirement is equivalent to the maintenance of a comprehensive
measure of wealth, where an economy’s wealth is defined to be the social worth
of its entire array of capital assets, including natural capital. Using data published by the World Bank on the world’s poorest regions, countries which would be regarded as having performed well if judged on the basis of such indices as GNP
per head or the Human Development Index are found to have grown poorer, a few alarmingly so.