**Average population **is the number of people on average for an entire period (usually a solar calendar year), calculated by the following formula:

P_{t} = P_{0 }× e^{rt}

In which:

– P_{t}: Average population of calculated year;

– P_{0}: Base year population;

– e: Natural logarithm, e = 2.71828;

– r: Population growth rate between the calculated time as compared to the base time;

– t: Time duration from base time to calculated time (Number of calculated years).

** Urban population** is the population of the territorial units which is designated as urban areas by the State (wards, town).

** Rural population** is the population of the territorial units which is designated as rural areas by the State (communes).

**Population density** is the average number of people per square kilometer of the territorial area, calculated by dividing the population (time point or average) of a certain residential area to the area of that territory. Population density can be calculated for the entire country or region (rural, urban, economic zone), in each province, district, commune, etc. to reflect the population distribution by geography at a given time.

Population density (persons/km |
= | Population (persons) |

Territorial area (km |

**Sex ratio of the population** reflects number of males per 100 females. Sex ratio of the population is determined by the following formula:

Sex ratio of the population | = | Total of males | × 100 |

Total of females |

**Sex ratio of newborns **also known as the **sex ratio at birth** reflects balance of the sex of newborns in a period. Sex ratio of newborns is calculated as the average number of boys per 100 girls who were born in the period:

Sex ratio of newborns |
= | Total male newborns in a period | × 100 |

Total female newborns in a period |

**Crude birth rate:** The indicator measures the fertility of the population, is one of the two components of natural population increase. High or low value of crude birth rate can affect the size, structure and population growth rate. Crude birth rate indicates that for every 1,000 people, how many live births are in the reference period.

**Total fertility rate (TFR) **reflects the average number of live births that would be born per woman (or a group of women) during the childbirth period if the woman (or a group of women) passes age-specific fertility rates observed in a given reference period during the reproductive period (aged 15 to 49).

**Crude death rate** is one of the two components of natural population increase. High or low value of crude death rate can affect the size, structure and population growth rate. Crude death rate indicates that for every 1,000 people, how many deaths are in the reference period.

**Infant mortality rate **is the measure of the mortality level of children in the first year of life. This rate is defined as the number of children under one year of age per 1,000 live births in the reference period on average.

**Under five mortality rate** is the measure of mortality level of children in the first five years of life. This rate is defined as the number of deaths of children under age 5 per 1,000 live births in the reference period on average.

**Population growth rate**

** Natural growth rate of population** is the difference between number of live births and number of deaths compared to the average population during the reference period, or the difference between the crude birth rate and the crude death rate of population in the reference period.

** Total growth rate of population **(or “population growth rate”) reflects the increase or the decrease of the population in reference period expressed as a percentage.

**Migration rates**

** In-migration rate** reflects the number of people from different territorial units (out-migration place) in-migrates to a territorial unit in the reference period on average per 1,000 population of that territorial unit (in-migration place).

** Out-migration rate** reflects the number out-migrants of a territorial unit in the reference period on average per 1,000 population of that territorial unit.

** Net-migration rate** reflects the status of in-migration and out-migration of population into/out from a territorial unit in the reference period. It is the difference between number of in-migrants and number of out-migrants of a territorial unit on average per 1,000 population of that territorial unit.

Data on In-migration rate, Out-migration rate and Net-migration rate of the whole Country, 6 socio-economic regions and 63 provinces/cities under the Central is only calculated for internal migration (not including international migration).

**Life expectancy at birth** reflects the prospect of a newborn could live for how many years if the current mortality model is maintained, this is the key statistical indicator of the Life table.

Life expectancy at birth is one of the integrated indicators calculated from the Life table.

The Life table is a statistical table that includes the indicators showing the viability of population moving from one age to the next and the mortality of the population at different ages. The Life table shows that from an initial set of the births (on the same cohort), there will be how many persons who will live to 1 year, 2 years, …, 100 years,…; among them, there are how many persons at each of the certain ages who will be dead before the following age; those persons who have reached a certain age will have what probability of survival and death; how long is the life expectancy in the future.

**Rate of literate population aged 15 and over** reflects the ability of reading and writing of the population, serves to assess the development level of a country, region or locality.

This indicator is calculated as the rate between the number of persons aged 15 years and over at specific time who are literate (able to read, write and understand a simple sentence in the national language, ethnic or foreign language) and the total population aged 15 years and over at that time.

Rate of literate population aged 15 years and over (%) |
= | Literate population aged 15 years and over | × 100 |

Total population aged 15 years |

**Number of divorce cases in a reference period **(usually a calendar year) is the number of cases which have been cleared up for couples to get divorce under the Marriage and Family Law in that period or year. Number of divorce cases does not include the cases of legal separation couple.

**Singulate mean age at marriage** (SMAM) reflects the average number of single life years of a presumptive cohort that has been lived single life before getting married for the first time, with the assumption that this cohort’s proportion of single by age is the same as the one collected at the intercensal time point.