Produces statistical indicators of the impact of migration on the socio-demographic
composition of an area. Three measures can be used: ratios, percentages and the Duncan index
of dissimilarity. The input data files are assumed to be in an origin-destination matrix format,
with each cell representing a flow count between an origin and a destination area. Columns are expected
to represent origins, and rows are expected to represent destinations. The first row and column are
assumed to contain labels for each area. See Rodriguez-Vignoli and Rowe (2018)