In Russia a "census" is understood to mean polling of all the country's population in the shortest possible time or "in one moment". That moment may in fact be a week or a month, but in any case the answers are collected at the so-called "census moment".

This is the most usual method of taking a census in all countries and is recommended by the UN Statistical Commission. The results of such "conventional" censuses provide the most complete data, which can be easily compared with information collected in other countries.

However, some countries use "alternative" ways of conducting censuses.

One of these is "registry census" where all the information obtained by various state registries is merged into a single database. Such an approach is used in the countries of Northern Europe. It may seem to be easier and more convenient, but that is not always the case. Firstly, the databases may have different formats, leading to errors when they are merged. Secondly, a census carried out using the registry method cannot test the data it deals with: an error in one of the public registries is unlikely to be discovered. Thirdly, even in Scandinavia public registries do not contain all information on the population: level of education, language proficiency and many other data cannot be obtained without actual polling of people.

«Different countries, different censuses»

A floating population census is used in France. A census poll is held every year in settlements with more than 10,000 residents, but it covers only 8% of households. Smaller settlements are broken down into five groups, and a census is taken once in five years for each group. So 40% of the population of medium-sized and large cities and all residents of small settlements and communities are polled in each five-year cycle, representing a total 70% of the country's population.

Various combinations of these different models are used in other countries. It could be said that Russia also uses elements of "registry censuses": during population surveys information about the material used for wall construction in apartment buildings is taken from documents held by municipalities.