Research on policy evaluation has gained in importance since the European Union introduced its new procedures on impact assessments in 2003. In the course of the EPOS project, the Institute for Ecological Economy Research (IOEW) and Ecologic Institute were organising the conference "Sustainable Development in Policy Assessment – Methods, Challenges and Policy Impacts", which took place from 15 until 16 June 2009 in Brussels. The conference seeked to contribute to the understanding of sustainability evaluation. Therefore, contributions were invited that tackle methodological challenges to sustainability evaluation, as well as the question of how the institutionalisation of sustainability evaluation can be improved.

Moreover, the submission of case studies on the role of impact assessments and evaluation studies on different topics (e.g. chemical or energy policy) in political decision-making processes was welcomed, which illustrate experiences, policy impacts, and the challenges of evaluation.

There are two main causes for the increasing significance of policy evaluation. First, during the late 1990s, environmental policy has come under more pressure to justify and explain its necessity; evaluations are thus seen as a tool to increase their legitimacy. Secondly, the drive towards "better regulation" at the European and national level has promoted evidence-based decision making and learning policy approaches. Regular evaluations are part of such learning policy approaches, with the aim to understand impacts at an early stage in order to enable corrections. This requires evaluations at different points of time: ex-ante, during the process, and / or ex-post. To be effective, the results of such evaluations have to be translated into politically acceptable measures. This, however, requires that environmental, economic and social aspects are integrated into different scientific disciplines and methods, such as academia, politics, administration and the broader public. Further, the findings need to be integrated into political decision, planning and implementation processes.

To further develop the different methods, the following challenges have to be met:

• The combination of different methods and benchmarks within the evaluation of policy actions, for example monetary judgement, quantitative but non-monetised judgement with physical indicators, qualitative judgement and participatory approaches.
• The valuation of policy actions increasingly takes place on a higher administrative level. At the same time, the analytical framework has been broadened from environmental impact assessments to sustainability impact assessments. Finally, the focus of valuation moves from single project and policy actions to the strategic level of programmes and policies.
• Furthermore, the question arises of how evaluation improves the quality of political decision-making. Understanding the influence of evaluation on decision-making is particularly important in this respect. Furthermore, the question arises of how evaluation findings should be fed back into the policy process. The comparison of ex-ante and ex-post evaluation provide further insights.

Besides addressing these research issues, the support by the German Ministry for Education and Research enabled Ecologic Institute to deepen and reinforce existing links with other European research institutes working on environmental policy evaluation, with the ultimate objective of creating a European network of such institutions.