Policy Impact Assessments (IA) are formalized, knowledge and evidence-based procedures to assess the intended and unintended, positive and negative impacts of policy proposals on economic, social, and environmental aspects, to inform policy development. They have been introduced in all OECD countries and the European Commission by now.
Key types of impact assessment include global assessments (global level), policy impact assessment (policy level), Strategic environmental assessment (programme and plan level), and Environmental impact assessment (project level). Specific thematic types of impact assessment are for instance Social impact assessment or gender impact assessment.
IAs can potentially improve the of legislation by:
- informing decision-makers about possible ramifications of the policy initiative on the economy, social and environmental issues, strengthening the evidence-basing of policies;
- improving the transparency of decision-shaping processes through the analysis of policy proposals’ likely effects, so that contributions to sustainability and ‘better regulation’ are disclosed while the pursuit of particular interests is made more difficult;
- increasing participation in the decision-making processes, in order to reflect a wide range of considerations and improve acceptance and legitimacy of the polciy; and
- making clear how policy proposals contribute to the various priorities, goals, and indicators of policy, thereby supporting achievement of goals.
- contributing to a continuous learning process in policy development: IA identifies causalities which can feed into the ex-post review of policies.
The department which is responsible for the policy proposal usually has to carry out the IA. Although the purpose and orientation of IA procedures differ, IA guidelines in the various jurisdictions all follow a similar set of steps to be followed by desk officers:
- Planning of the IA
- Carrying out the impact analysis
- Consultation of affected stakeholders and the general public
- Coordination with other affected departments
- Summary and presentation of findings in an IA report
- Forwarding of IA findings to decision-makers
- Publication of the IA report (not in all countries).
The analytical steps, which mainly relate to step 2, can be set out as i. Problem definition ii. Definition of policy objectives iii. Development of policy options iv. Analysis of impacts v. Comparison of policy options and recommendation of one option vi. Defining monitoring measures.
Methods for Supporting Policy Impact Assessment
Throughout the IA process, methods can be used for support. In recent years governments have increasingly invested in developing and applying methods and tools for IA.  Depending on their usage in the various IA steps, methods for IA can be classified as methods for
- Scoping (e.g. checklists)
- For qualitative analysis (e.g. focus groups)
- For quantitative analysis (e.g. life-cycle assessment, material flow accounting, modelling)
- Aggregation and comparison of options (e.g. CBA)
- Analysing the coherence of policies (e.g. Gender IA)
- Supporting participation and involvement (e.g. internet consultation)
- Data presentation and involvement (e.g. GIS)
- Monitoring and evaluation (e.g. indicators) 
- Social impact assessment
- Environmental impact assessment
- Life Cycle Impact Assessment
- Outcomes theory
- Policy studies
- Policy analysis
- Participatory Impact Pathways Analysis
- Program evaluation
- Impact evaluation
- Adelle, Camilla; Weiland, Sabine (2012). "Policy assessment: the state of the art". Impact Assessment and Project Appraisal 30 (1): 25–33. doi:10.1080/14615517.2012.663256.
- Jacob, Klaus; Ferretti, Johanna; Guske, Anna-Lena; Turnpenny, John; Jordan, Andrew; Adelle, Camilla (2011). "Sustainability in Impact Assessments A Review of Impact Assessment Systems in selected OECD countries and the European Commission". OECD. SG/SD(2011)6/FINAL. Retrieved 10-12-2012. Check date values in:
- Podhora, Aranka; Helming, K, Adenäuer, L., Heckelei, T., Kautto, P., Reidsma, P., Rennings, K., Turnpenny, J. and Jansen, J. (2013). "). The policy-relevancy of impact assessment tools: Evaluating nine years of European research funding". Environmental Science & Policy 31: 85–95. doi:10.1016/j.envsci.2013.03.002.
- Nilsson, Mans; Jordan, Andrew; Turnpenny, John; Hertin, Julia; Nykvist, Björn; Russel, Duncan (2008). "The use and non-use of policy appraisal tools in public policy making: an analysis of three European countries and the European Union". Policy Sciences 41: 335–355. doi:10.1007/s11077-008-9071-1.
- LIAISE - Network of Excellence. "LIAISE KIT - Knowledge for Decision Making". Retrieved 03-05-2013. Check date values in: