aggregate numbers of migrants into or out of a country. These can either be
totals (e.g. 20,000 new migrants arrived in the UK in 2017) or could be broken
down (e.g. of the 20,000 migrants to the UK in 2017, 7,000 were from Spain).
Flows can also be ‘netted’ so that you look at the difference between those
people arriving as migrants and those leaving a country. This gives a net
migration flow which could either be positive (more arriving than leaving),
negative (more leaving than arriving) or balanced (as many leave as arrive).