The term migration data refers to “all types of data that would support the development of comprehensive, coherent and forward-looking migration policies and programming, as well as contribute to informed public discourse on migration. This includes data concerning different forms of population movement, including short and long-term, forced and voluntary, cross-border and internal, as well as data concerning characteristics of movement and those on the move, reasons for and impacts of migration” (IOM, 2021a:2). Migration data also include relevant data relating to migrants and migration from related policy sectors, such as the labour market, health and education.
Data can be recorded as quantitative or qualitative data. Quantitative data consist of numerical and quantifiable evidence which help to understand the incidence and rate at which a phenomenon is occurring, showing trends and enabling projections. Qualitative data are descriptive and collected using techniques such as interviews or focus groups (IOM, 2024a). While the focus of the Essentials of Migration Data (EMD) is largely on quantitative data and data sources, qualitative data remain equally important for several reasons: they provide a bottom-up or grassroots perspective of the concepts measured by survey instruments; they can inform the design of quantitative survey instruments; they can raise the voices of marginalized individuals and provide information regarding practices or policies that differentially impact migrants; and they illustrate the mechanisms or processes underlying the patterns or trends observed through quantitative data (IOM, 2021b).
Statistics is a field of mathematics that involves collecting, describing, analysing and interpreting quantitative data. Whereas descriptive statistics describe the properties of a given sample of observations, inferential statistics use those same properties in order to test hypotheses about mechanisms underlying observed patterns or trends in the data. Statistical analysis is the application of mathematical techniques to draw conclusions about a larger population on the basis of a smaller sub-sample (Michigan Tech, 2022). When migration data are collected, described and analysed using statistical methods, they become known as migration statistics. Migration statistics have strong implications for policymaking, human resources, human rights and politics, some of which will be illustrated in this the EMD (IOM, 2024a).