A second approach has been suggested based on economics and the social welfare function. To calculate the social welfare function requires an aggregation of the impacts of climate change policies and climate change itself across all affected individuals. This calculation involves a number of complexities and controversial equity issues (Markandya "et al.", 2001:460). For example, the monetization of certain impacts on human health. There is also controversy over the issue of benefits affecting one individual offsetting negative impacts on another (Smith "et al."., 2001:958). These issues to do with equity and aggregation cannot be fully resolved by economics (Banuri "et al."., 1996:87).