In short, there is progress through contractual approaches and collective learning processes, albeit too slow. Most experts now agree on the need to supplement regulations and voluntary agreements with general economic incentives, i.e. abstraction and pollution charges, in particular on farmers, the former to be paid by volumes abstracted. However, through a direct application of Ronald Coase’s theorem on solving the social cost problem, one can easily foresee an outcome more on the subsidy than on the taxing side: the value of potable water is so much higher than that of agricultural water or the added value of fertilisers, that water suppliers generally can buy the farmers losses from reextensification. Water suppliers are increasingly concerned by the rising levels of fertilisers and pesticides in groundwater, and they have started making local contracts with farmers to "buy up their pollution".