Two censuses were held in the Soviet Union shortly before World War II, in 1937 and 1939. Preparation for the census commenced as far back as 1932, as resolved by the national government (the Council of People's Commissars).

Rapid industrialisation, migration of people from the country to urban areas, as well as administrative and territorial reforms made it difficult to obtain an accurate count of the population not only in regions, but even in cities and towns.

«It is difficult to know the real number of regions»

On this occasion politicians interfered with the work of statisticians: an ad-hoc commission chaired by Vyacheslav Molotov, Head of the Soviet Government, was set up in September 1935 to finalize the program and the census toolkit. Many issues that could expose serious problems in the country were removed from the census program.

The census took place on January 6, 1937, but difficulties began when the first data from the population census began arriving at the center: many settlements proved to have fewer people than in the previous count.

The extreme politicization of the census had tragic results: materials of the census were officially labeled as "defective". They were classified and then destroyed. Many statisticians were imprisoned or executed, including Ivan Kraval, Head of the Statistics Bureau, who was executed by firing squad on 26 September 1937 and exonerated only in 1956.

«A new census in a short time frame»

It was then decided to hold a new census on 17 January 1939. Preparations were made in great haste. The census was strictly organized; out of some half a million census takers, only 1187 failed to begin work at the appointed time, mainly due to illness.

The results were processed using mechanisation at three "factories" in Moscow, Leningrad, and Kharkiv. The census forms were encrypted at special encryption bureaus set up at 45 republican, territorial, and regional statistics services before their delivery to the mechanised counting factories.

The preliminary results of the census were reported to Joseph Stalin and Vyacheslav Molotov as early as 10 February 1939. The final note signed by Ivan Sautin, Head of the Central Directorate for National Accounting, stated that the total population of the USSR was estimated at 167.3 million.

On 10 March, speaking at the 18th Congress of the Soviet Communist Party, Stalin reported that 170 million people resided in the Soviet Union, which is almost the exact figure shown afterward in the official census results: 170,557,093 persons.

Preliminary results of the 1937 census had shown that the country had 162 million residents, so the new census suggested an increase of more than 5%. Publication of a compendium of census results was cut short by the outbreak of war in 1941. The materials were partially published in 1956, but complete data were only issued in the compendium of 1992.