the new data , released by the united nations , shows how the number of international migrants has increased by nearly 80 million over the last 25 years .
in comparison , that number had risen to 231 million globally by 2013 , according to the international migrant stock trends data .
the graphic , featured in the telegraph , comes at a time when immigration is being heavily discussed by political parties , who each have varying policies on the issue in their manifestos that