A three-year comparative longitudinal study of a school-based social work family service to reduce truancy,delinquency and school exclusions

New Labour is keen to use legislation to encourage what are seen as desirable family practices, and to discourage other, less-favoured, forms. What this means in policy terms has now been codified in its 1998 Green Paper, Supporting Families . In this paper, we examine the validity of this enterprise in terms of its underlying assumptions about social behaviour and economic decision making. We argue that the government implicitly assumes a universal model of 'rational economic man' and his close relative the 'rational legal subject', whereby people take individualistic, cost-benefit type decisions about how to maximize their own personal gain. Change the financial structure of costs and benefits, and the legal structure of rights and duties, in the appropriate way and people will modify their social behaviour in the desired direction. However, recent research suggests that people do not act like rational economic man in making decisions about their moral economy. Legislation based on this assumption might then be ineffectual and the proposals in Supporting Families seem to be one example. This is what we have labelled the 'rationality mistake'. In Part I of this work, we focus on the financial proposals in the Green Paper and on the New Deal for Lone Parents in particular. We then go on to counterpose this with the results of recent empirical work on how and why people actually do make family decisions. In Part II, to be published in the next issue, we focus on chapter four of Supporting Families , on strengthening marriage, and again compare New Labour's proposals with recent empirical work.