Resource intensity is a measure of the resources (e.g. water, energy, materials) needed for the production, processing and disposal of a unit of good or service, or for the completion of a process or activity; it is therefore a measure of the efficiency of resource use. It is often expressed as the quantity of resource embodied in unit cost e.g. litres of water per $1 spent on product. In national economic and sustainability accounting it can be calculated as units of resource expended per unit of GDP. When applied to a single person it is expressed as the resource use of that person per unit of consumption. Relatively high resource intensities indicate a high price or environmental cost of converting resource into GDP; low resource intensity indicates a lower price or environmental cost of converting resource into GDP.