Factors affecting the population change in a region are birth rate, death rate, and migrations. The birth rate is a statistic that measures the number of live births per 1000 people. The death rate is a statistic that measures the number of deaths per 1000 people. Along with birth and death rate, another factor affecting population change is migration. Migration refers to the movement of people from one area to another. People leaving a country are called emigrants and the phenomenon is called emigration. People arriving in a country are called immigrants and the phenomenon is called immigration.