The Kingdom of Yugoslavia existed between its creation in 1918 until its occupation and partition by Axis powers in World War II. The first census in 1921 enumerated 11,984,911, while the second and last census in 1931 enumerated 13,934,038 people. While both censuses grouped ethnic groups according to their mother tongue, the latter did not record separate constituent nationalities and reported all "Serbo-Croato-Slovene" speakers as "Yugoslavs".
1 Source: Banac, Ivo (1992). The National Question in Yugoslavia. Origins, History, Politics (2nd printing ed.). Ithaca, NY: Cornell University Press. p. 58. ISBN 9780801494932. (The table represents a reconstruction of Yugoslavia's ethnic structure immediately after the establishment of the kingdom in 1918.)
Based on language, the Yugoslavs (collectively Serbs, Croats, Slovenes and other South-Slavic groups in the kingdom) constituted 82.9% of the country's population.
^ abBanac, Ivo. The National Question in Yugoslavia: Origins, History, Politics. Archived 2 August 2020 at the Wayback Machine Cornell University Press, 1988. pp. 49–53, 58. ISBN 978-0801494932
^Per Banac himself, the Macedonians were "Bulgarians in the common struggle against Serbian and Greek hegemonism, but within the Bulgarian national project, they were increasingly becoming separate regional community." The National Question in Yugoslavia: Origins, History, Politics. Cornell University Press, 1988. p. 327. ISBN 978-0801494932
^RÉSULTATS DÉFINITIFS DU RECENSEMENT DE LA POPULATION DU 31 JANVIER 1921 (in Serbo-Croatian and French). Sarajevo: Opšta državna statistika. 1932. p. 3.
^ abcdefgh"2-1. Kretanje stanovništva 1921–1990 - Jugoslavija". Demografska statistika 1990(PDF). Belgrade: Savezni zavod za statistiku. 1992. ISSN 0084-4357. Retrieved 27 January 2023.
^"Statistical Yearbook of the Kingdom of Yugoslavia,1929" (PDF). Archived (PDF) from the original on 2 August 2020. Retrieved 8 May 2020.
^"Statistical Yearbook of the Kingdom of Yugoslavia,1937" (PDF). Archived (PDF) from the original on 2 August 2020. Retrieved 8 May 2020.
^"Statistical Yearbook of the Kingdom of Yugoslavia,1938-1939" (PDF). Archived (PDF) from the original on 2 August 2020. Retrieved 8 May 2020.
^"Statistical Yearbook of the Kingdom of Yugoslavia,1940" (PDF). Archived (PDF) from the original on 2 August 2020. Retrieved 8 May 2020.
^ abGroup of Authors (1997). Istorijski atlas (1st ed.). Zavod za udžbenike i nastavna sredstva & Geokarta, Belgrade. p. 91. ISBN 8617055944.
^""Краљевина Југославија дефинитивни резултати пописа становништва од 21 јануара 1921 год.", Сарајево, Државна Штампарија, 1932". p. 3. Archived from the original on 3 November 2013. Retrieved 1 November 2013.
^Group of Authors (1997). Istorijski atlas (1st ed.). Zavod za udžbenike i nastavna sredstva & Geokarta, Belgrade. p. 86. ISBN 8617055944.