Today, we studied for the test on Friday, which is about population and migration. Here are what we reviewed today. Life expectancy: a average of number of years to be lived by a group of people who was born in particular area and particular year. Crude birth rate: number of births per 1000 people in a given country in a year. Crude death rate: number of births per 1000 people in a given country in a year. Developed country: a country that gas a highly developed economy and advanced technological infrastructure relative to other less industrialized nations. Developing country: a country with a lower living standard, underdeveloped industrial base, and low Human Development Index relative to other countries. Rate of natural increase:the difference between crude birth rate and crude death rate. Immigration: a number of people coming into the country. Emigration: a number of people leaving the country. Net migration rate: a number of people leaving or coming into a country per 1000 people in a year. Push force: the factors that make people leaving the country. Pull force: the factors that make people coming into the country.