In either case, further monitoring and research are needed to understand the underlying causes. Indicators offer a measure of the effectiveness of actions in moving a system towards a more desirable state. For example, if body temperature decreases after taking a medicine, we conclude that the medicine has been effective in combating the disease. To accomplish this objective, indicators should provide an ability to assess cause-and-effect relations. They help policy makers and the public to understand the linkages and trade-offs between economic, environmental and social values in order to evaluate the long-term implications of current decisions and behaviour and to monitor progress towards sustainable development goals by establishing baseline conditions and trends.