In the space available it is possible to provide onlythe briefest insight into the use of CBA in the USA.None the less, some reference is essential to set thescene for the UK analysis.In the USA CBA developed beyond the 1950s focuson water resources, extending into most areas ofpublic policy including education and health. Amajor impetus to CBA came with the ReaganAdministration. Within weeks of taking office in1981, President Reagan issued Executive Order12291, requiring a CBA for all new major regula-tions. The order required, among other things, that‘regulatory objectives shall be chosen to maximizethe net benefits to society’, and that, for givenregulatory objectives, ‘the alternative involving theleast net cost to society shall be chosen’. As Smith(1984) notes, this did not mean that CBA wascarried out consistently or universally. Substantialareas of regulation are not subject to CBA. Indeed,some regulations explicitly forbid an appraisal ofcosts and benefits. Court rulings have also estab-lished that where the original enabling legislationdoes not mention costs and benefits, agencies maynot consider them (for a detailed description ofwhich environmental legislation is subject to CBA,see Morgenstern, 1997). None the less, CBA playsa significant role in regulatory assessment. In con-trast, as we shall see, there has been a cautious trendin the UK towards a general requirement for somesort of regulatory CBA, but nothing as precise asthe US legislation.Much of the stimulus to CBA in the USA came, asit had in the 1950s, from a concern about efficiencyin government. But whereas the earlier concernrelated to a real scarcity of government funds andpolitical concerns with major investments, the 1980sand 1990s focus was on regulation. In particular,there was a political backlash against perceivedexcessive regulation and against clear inconsisten-cies and irrationalities in public controls. In the viewof those concerned about regulation, CBA wouldhelp to prevent over-regulation. In the environmen