The ecological footprint is a method promoted by the Global Footprint Network to measure human demand on natural capital, i.e. the quantity of nature it takes to support people and their economies. It tracks this demand through an ecological accounting system. The accounts contrast the biologically productive area people use for their consumption to the biologically productive area available within a region, nation, or the world (biocapacity, the productive area that can regenerate what people demand from nature). In short, it is a measure of human impact on the environment and whether that impact is sustainable. Footprint and biocapacity can be compared at the individual, regional, national or global scale. Both footprint and demands on biocapacity change every year with number of people, per person consumption, efficiency of production, and productivity of ecosystems. At a global scale, footprint assessments show how big humanity's demand is compared to what Earth can renew. Global Footprint Network estimates that, as of 2019, humanity has been using natural capital 75% faster than Earth can renew it, which they describe as meaning humanity's ecological footprint corresponds to 1.75 planet Earths. This overuse is called ecological overshoot. Ecological footprint analysis is widely used around the world in support of sustainability assessments. It enables people to measure and manage the use of resources throughout the economy and explore the sustainability of individual lifestyles, goods and services, organizations, industry sectors, neighborhoods, cities, regions, and nations. The first academic publication about ecological footprints was written by William Rees in 1992. The ecological footprint concept and calculation method was developed as the PhD dissertation of Mathis Wackernagel, under Rees' supervision at the University of British Columbia in Vancouver, Canada, from 1990 to 1994. Originally, Wackernagel and Rees called the concept "appropriated carrying capacity".