Human population Factors affecting human population size -Birth rate    The birth rate isthe number of live babies born ina year for every 1000 people.   A high birth rate:    -Early marriges    -Lack of knowledge of birth control -Death rate The death rate is the number of people dying in a year for every 1000 people.   A high death rate:    -diseases     -famine    - natural disasters -Decrease in population size   A people considered ageing when:    -people under the age of 15 make less than 30% of the population.    - people above the age of 65 make up more than 6% of the population. People density Human migration is human movement from one area to another. Immigration Immigration takesplace when people move to another country permanently. Emmigration Emigration takes place when people move out of the country permanently.