The attempt to compare the total social costs and benefits of implementing a decision, usually expressed in money terms; ‘the decision-making tool of choice in contested planning decisions’ (J. Adams 1995). Costs and benefits include money, externalities—for example pollution, noise, and disturbance to wildlife—and external benefits, such as reductions in travelling time or traffic accidents. Rouwendal and van der Straaten (2008) CPB Disc. Papers 98 note that ‘when costs and benefits of actual projects are listed and have to be traded off against each other as to determine the net result, consensus often disappears’. They discuss a hedonic method as an attempt to compute the monetary value of the benefits objectively. Hanley et al. (2003) J. Env. Manag. 68, 3 observe that decisions over the size of the population affected are crucial in the calculation of aggregate benefits and costs. Castree (2003) PHG 27, 3 argues that cost–benefit analysis is one mechanism of ‘achieving proxy commodification and can serve as [a precursor] to the creation of real markets’. See A. Boardman et al. (2006).