ABSTRACT
Since the 1992 Earth Summit in Rio, there have been many initiatives to promote and measure sustainable development (UN, 1992). Indicators of the degree of sustainability are widely regarded as useful tools for gaining insight about the progress made towards achieving sustainable development. They are a flexible means of producing quantified or quantifiable information that can be readily understood and used by a range of specialists. They are not, in themselves, statistics, standards or criteria; rather, they are a way of ordering information in order to give a synoptic view of a situation or a process. Among the main functions of indicators proposed by the Organisation for Economic Co-operation and Development (OECD) are simplification, showing changes over time; quantification, based on theory and science; reliability and information; and ability to update. However, ease of understanding by general users is also important (OECD, 1978, 1997a).
