Analysing spatial interactions: inter-regional migration flows

Spatial variations in social phenomena are often the product of interactions or flows between places. Migration flows, for example, are the primary cause of inter-regional differentials in population growth and age composition. In many areas of geography, it is the flows themselves that are of interest – of goods and services, of communications, of trade and of people. Such flows effectively underpin almost every aspect of human activity – economic, social, demographic and political – and, of course, they are of interest more widely in the social sciences. Technically, these flows between places represent spatial interactions which can be measured in a variety of ways using different zonal systems and observation intervals: the zonal system refers to the way in which the geographic area is disaggregated into geographic units – the number of zones and the shape into which the space is divided; and the observation interval refers to the time period over which the interactions are measured. In practice, these aspects of the flow matrix – the type of data, the zonal system and the observation interval – have significant implications for the results obtained from any analysis. There is an extensive literature in geography and regional science focusing on different forms of interaction at various spatial scales (local, regional, global) over widely varying time periods: trade and commodity flows, communications, tourist movements, airline flights, and so on