As the name suggests, this study typically tracks the flow of a specific substance through a defined socio-economic system in an attempt to quantify the flow of this substances. For example, a case study in Cape Town, South Africa demonstrated varying concentrations of in-use copper stocks throughout the city. Mapping these concentrations enabled analysis of differences in copper use among neighbourhoods to show how wealth and class affects copper stocks and flows. As a result, the study revealed that policies aimed at reusing copper in Cape Town should be aimed at poorer residential and industrial areas given the high concentration of copper in these areas.