Collecting evidence: Ingredients of scenario-building

In this chapter, we outline the elements of the scenario-building process detailed throughout the whole book. We distinguish various objectives of forward-looking exercises, from prediction to preparedness and building resilience. We discuss how the two types of uncertainty - epistemic and aleatory - shape these objectives in different ways. For epistemic uncertainty, we show how and where it can be reduced by better conceptualization, sharper theoreticalExplanations explanations, and better evidence on international migration and its drivers. Moving to irreducible aleatory randomness, we discuss its possible sources, focusing on human agency and the role of unforeseen events. We also present the implications for policymakers and migration practitioners that arise from responding to the challenges brought about by uncertainty around migration flows.