Other factors such as mass migration out of China must be taken into account.

Mass migration - slavery - took place to America 400 years ago.

There has been mass migration out of Liverpool, which lost 330,000 people over the last 50 years.

Mass migration from Asia has reinvigorated the street scene in recent years.

Mass migration had almost overnight made blacks America's most urban ethnic group.

Mass migration of people started in late 1950s.

Mass migrations of immigrants to the United States came in several waves.

Mass migration of peoples is nothing new -it has been going on since time immemorial.

Mass migration has made this difficult to achieve.

Even more combustible is the issue of ethnicity and race as mass migration becomes part of global life.