when economic activity becomes less intensive ecologically: A declining input of natural resources is needed to produce one unit of output on average, measured by the ratio of total natural resource consumption to gross domestic product (GDP). Relative resource decoupling occurs when natural resource consumption declines on a ceteris paribus assumption — that is, all other things being equal. Absolute resource decoupling occurs when natural resource consumption declines, even while GDP is growing. In the history of economic thought, William Stanley Jevons was the first economist of some standing to analyse the occurrence of resource decoupling, although he did not use this term. In his 1865 book on The Coal Question, Jevons argued that an increase in energy efficiency would by itself lead to more, not less, consumption of energy: Due to the income effect of the lowered energy expenditures, people would be rendered better off and demand even more energy, thereby outweighing the initial gain in efficiency. This mechanism is known today as the Jevons paradox or the rebound effect. Jevons's analysis of this seeming paradox formed part of his general concern that Britain's industrial supremacy in the 19th century would soon be set back by the inevitable exhaustion of the country's coal mines, whereupon the geopolitical balance of power would tip in favour of countries abroad possessing more abundant mines. In 2009, two separate studies were published that — among other things — addressed the issues of resource decoupling and the rebound effect: German scientist and politician Ernst Ulrich von Weizsäcker published Factor Five: Transforming the Global Economy through 80% Improvements in Resource Productivity, co-authored with a team of researchers from The Natural Edge Project. British ecological economist Tim Jackson published Prosperity Without Growth, drawing extensively from an earlier report authored by him for the UK Sustainable Development Commission. Consider each in turn: Ernst Ulrich von Weizsäcker argues that a new economic wave of innovation and investment — based on increasing resource productivity, renewable energy, industrial ecology and other green technology — will soon kick off a 'Green Kondratiev' cycle, named after the Russian economist Nikolai Kondratiev. This new long-term cycle is expected to bring about as much as an 80 percent increase in resource productivity, or what amounts to a 'Factor Five' improvement of the gross input per output ratio in the economy, and reduce environmental impact accordingly, von Weizsäcker promises. Regarding the adverse rebound effect, von