Thirteen years after Poland regained independence, on December 9, 1931, the Second General Census was conducted.

The census was conducted on the basis of the act of October 14, 1931. The act determined the date of the next census and confirmed that the censuses would be organized every 10 years (the next one was planned in 1941, but it was not held because of the war, and the next census - a aggregated one - was not conducted until February 14, 1946). The range of the census and organization were defined in the regulation of the Council of Ministers of September 2, 1931.

The organization, legal rules, duties and tasks of the Census Services was a continuation of the solutions from 1921, and the subject area was basically the same.

During the Second General Census of 1931, as in the census of 1921, the population was examined on the basis of religion and mother tongue. In comparison with the First General Census of 1921, several changes were made to the questionnaire, incl. the question of nationality has been removed and the question of literacy has been added.

A novelty in this census was the importance attached to the tasks, responsibilities and powers of the census commissioners (today's enumerators). Each census commissioner (today called a census taker) received a personal identity card, which made him a "civil servant on duty". The data collected were subject to strict statistical confidentiality.

1931 Census Services, just like us today, attached great importance to the popularisation of the census. Hence, the excellent leaflet "What will the second census give us? was in circulation - a skillful combination of information about the results of the 1921 census, explanations to the 1931 census and promotion of the very idea of the census. 

The first preliminary results of the Second General Census of 1931 were published by the Statistics Poland in the brochure of April 5, 1932. It contained data on the number of inhabitants of cities over 10.000 compared to the 1921 census.

The essential survey after the 1931 census covered the issues of housing, households, population and professional relations and was published for all voivodeships and the largest cities of Poland at that time (Warsaw, Cracow, Lwow, Wilno, Poznan and Lodz).

The final results were published in the series of publications "Statistics of Poland". The administrative division was applied on January 1, 1933 (for central and eastern voivodeships ) or on August 1, 1934 (for other voivodeships). Publishing of the series began in 1936 and was interrupted by the outbreak of Second World War. 39 volumes with detailed surveys of the 1931 census are now available in the Central Statistical Library also online.

Data on nationality,  mother tongue, religion, education, as well as demographic and labor market issues, collected during the census of 1931, still represent a valuable cognitive data science.