Beyond evidence-based policymaking? Exploring knowledge formation and source effects in US migration policymaking

Several scholars have observed persistent gaps between policy responses to complex, ambiguous and politicized problems (such as migration, climate change and the recent Covid-19 pandemic) and evidence or 'facts'. While most existing explanations for this 'evidence-policy gap' in the migration policy field focus on knowledge availability and knowledge use by policymakers, this article shifts the focus to processes of knowledge formation, exploring the questions of what counts as 'evidence' for migration policymakers and what are the sources of information that shape their understandings of migration policy issues. It does so, by developing a network-centred approach and focusing on elite US policy-makers in the field of irregular and asylum-seeking migration. This 'heuristic case' is used to challenge existing explanations of the 'evidence-policy gap' and to generate new explanations to be tested in future research. Our findings-based on qualitative and quantitative data collected in 2015-2018 through 57 elite interviews analysed applying social network analysis and qualitative content analysis-challenge scholarly claims about policymakers' lack of access to evidence about migration. We also challenge claims that migration-related decision-making processes are irrational or merely driven by political interests, showing that policymakers rationally collect information, select sources and attribute different relevance to 'evidence' acquired. We instead highlight that knowledge acquisition processes by elite policymakers are decisively shaped by dynamics of trust and perceptions of political and organizational like-mindedness among actors, and that political and ideological factors determine what qualifies as 'evidence' in the first place.