Weizsäcker notes that "... efforts to improve efficiency have been fraught with increasing overall levels of consumption." As remedies, von Weizsäcker recommends three separate approaches: Recycling of and imposing restrictions on the use of materials; establishing capital funds from natural resource proceeds for reinvestments in order to compensate for the future bust caused by depletion; and finally, taxing resource consumption so as to balance it with the available supplies. Tim Jackson points out that according to empirical evidence, the world economy has indeed experienced some relative resource decoupling: In the period from 1970 to 2009, the 'energy intensity' — that is, the energy content embodied in world GDP—decreased by 33 percent; but as the world economy also kept growing, carbon dioxide emissions from fossil fuels have increased by 80 percent during the same period of time. Hence, no absolute energy resource decoupling materialized. Regarding key metal resources, the development was even worse in that not even relative resource decoupling have materialized in the period from 1990 to 2007: The extraction of iron ore, bauxite, copper and nickel was rising faster than world GDP to the effect that "resource efficiency is going in the wrong direction," mostly due to emerging economies — notably China — building up their infrastructure. Jackson concludes his survey by noting that the 'dilemma of growth' is evident when any resource efficiency squeezed out of the economy will sooner or later be pushed back up again by a growing GDP. Jackson further cautions that "simplistic assumptions that capitalism's propensity for efficiency will stabilize the climate and solve the problem of resource scarcity are almost literally bankrupt." Herman Daly has argued that the best way to increase natural resource efficiency (decouple) and to prevent the occurrence of any rebound effects is to impose quantitative restrictions on resource use by establishing a cap and trade system of quotas, managed by a government agency. Daly believes this system features a unique triple advantage: Absolute and permanent limits are set on the extraction rate of, use of and pollution with the resources flowing through the economy; as opposed to taxes that merely alter the prevailing price structure without stopping growth; and as opposed to pollution standards and control which are both costly and difficult to enact and enforce. More efficiency and recycling efforts are induced by the higher resource prices resulting from the restrictions (quota prices plus regular extraction costs). No