Final answer:
The numerical difference between immigration and emigration is called net migration, with immigration being the influx to a country and emigration as the outflow from a country.
Step-by-step explanation:
The numerical difference between immigration and emigration is called net migration. Immigration refers to the movement of people into a country to live permanently, whereas emigration is the act of leaving one's own country to settle permanently in another. The concept of net migration is essential when analyzing population changes, as it reflects the actual change in population size due to the movement of people in and out of a country.
For example, if 100 people immigrate to a country and 50 people emigrate from that same country, the net migration would be 50 (100 immigrants - 50 emigrants). This means the population has increased by 50 people due to migration. Similarly, net migration could be negative if more people emigrate than immigrate, leading to a decrease in population.