Determination of the population size is carried out in the form of a periodic census or current registration. Each of the species has its own individual characteristics, the most important are the choice of the moment and the category of the population taken into account.
The population in all territories is constantly changing. This happens due to death, birth, migration, therefore, a certain period of time is predetermined for the accounting in order to most accurately reflect the demographic situation.
It is customary to carry out international accounting in the middle of the period, for example, in the middle of the calendar year. Then the average indicator is calculated from the recorded number of the population at the end and beginning of the current year.
In the Russian Federation, the population is recorded at the end of the reporting year. The results are carried over to the beginning of the next year. Census days are set by determining the lowest daily and annual mobility of the population, which is recorded by statistics.
When using various methods, the size of the census population can vary significantly, therefore, the census and census can be carried out strictly at the specified time.
In accordance with the data of state registration, three main categories of the population can be distinguished - permanent, legal, cash. The permanent population is persons who are in the region at the time of the census; the actual legal address of their permanent place of residence is not taken into account. The legal population is the person registered at the time of the census in a given region. The available population includes persons permanently or temporarily residing in the region.
In order to most accurately reflect the demographic situation, it is important to take into account the data of the existing population. The all-Russian population census takes into account the same parameters.
Accordingly, the demographic size of the population, which is most important to know, is determined based on the number of actual persons included in the census. The legal address and place of permanent residence are not taken into account, since it is not important.