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".
| Ethnic group | Number | Percent | |
|---|---|---|---|
| Serbs (including Montenegrins and some Macedonians) | 4,665,851 | 38.8% | |
| Croats | 2,856,551 | 23.8% | |
| Slovenes | 1,024,761 | 8.5% | |
| South Slavic Muslims | 727,650 | 6.1% | |
| Bulgarians (including some Macedonians[2]) | 585,558 | 4.9% | |
| Other Slavs | 174,466 | 1.5% | |
| Germans | 513,472 | 4.3% | |
| Hungarians | 472,409 | 3.9% | |
| Albanians | 441,740 | 3.7% | |
| Romanians and Cincari[3] (Aromanians and Megleno-Romanians) | 229,398 | 1.9% | |
| Turks | 168,404 | 1.4% | |
| Jews | 64,159 | 0.5% | |
| Italians | 12,825 | 0.1% | |
| Others | 80,079 | 0.7% | |
| Total | 12,017,323 | 100% | |
| 1 Source: Book: Banac, Ivo. Ivo Banac . The National Question in Yugoslavia. Origins, History, Politics. Cornell University Press . Ithaca, NY . 58 . 1992 . 2nd printing . 9780801494932. (The table represents a reconstruction of Yugoslavia's ethnic structure immediately after the establishment of the kingdom in 1918.) | |||
| Average population[4] | Live births | Deaths | Natural change | Crude birth rate (per 1,000) | Crude death rate (per 1,000) | Natural change (per 1,000) | Total fertility rate | ||
|---|---|---|---|---|---|---|---|---|---|
| 1919 | 11,706,957 | 347,748 | 258,638 | 89,110 | 29.7 | 22.1 | 7.6 | 4.83 | |
| 1920 | 11,881,764 | 422,267 | 250,090 | 172,177 | 35.5 | 21.0 | 14.5 | 4.79 | |
| 1921 | 12,059,178 | 442,530 | 252,104 | 190,426 | 36.7 | 20.9 | 15.8 | 4.75 | |
| 1922 | 12,239,245 | 420,910 | 254,478 | 166,432 | 34.4 | 20.8 | 13.6 | 4.70 | |
| 1923 | 12,421,997 | 432,779 | 252,543 | 180,236 | 34.8 | 20.3 | 14.5 | 4.66 | |
| 1924 | 12,607,480 | 442,835 | 254,527 | 188,308 | 35.1 | 20.2 | 14.9 | 4.62 | |
| 1925 | 12,795,732 | 437,070 | 239,429 | 197,641 | 34.2 | 18.7 | 15.4 | 4.57 | |
| 1926 | 12,986,796 | 459,035 | 244,761 | 214,274 | 35.3 | 18.8 | 16.5 | 4.53 | |
| 1927 | 13,180,709 | 451,617 | 276,294 | 175,323 | 34.3 | 21.0 | 13.3 | 4.49 | |
| 1928 | 13,377,523 | 437,523 | 272,606 | 164,917 | 32.7 | 20.4 | 12.3 | 4.44 | |
| 1929[5] | 13,577,272 | 452,544 | 286,249 | 166,295 | 33.3 | 21.1 | 12.2 | 4.40 | |
| 1930 | 13,780,006 | 489,270 | 261,497 | 227,773 | 35.5 | 19.0 | 16.5 | 4.36 | |
| 1931 | 13,982,000 | 470,275 | 276,840 | 193,435 | 33.6 | 19.8 | 13.8 | 4.31 | |
| 1932 | 14,174,000 | 465,935 | 272,180 | 193,755 | 32.9 | 19.2 | 13.7 | 4.27 | |
| 1933 | 14,369,000 | 452,229 | 243,717 | 208,512 | 31.5 | 17.0 | 14.5 | 4.22 | |
| 1934 | 14,566,000 | 460,913 | 248,882 | 212,031 | 31.6 | 17.1 | 14.6 | 4.18 | |
| 1935 | 14,767,000 | 441,728 | 248,978 | 192,750 | 29.9 | 16.9 | 13.1 | 4.14 | |
| 1936 | 14,970,000 | 435,861 | 240,879 | 194,982 | 29.1 | 16.1 | 13.0 | 4.09 | |
| 1937[6] | 15,172,000 | 424,448 | 242,337 | 182,111 | 28.0 | 16.0 | 12.0 | 4.05 | |
| 1938[7] | 15,384,000 | 411,381 | 240,303 | 171,078 | 26.7 | 15.6 | 11.1 | 4.01 | |
| 1939[8] | 15,596,000 | 403,938 | 233,196 | 170,742 | 25.9 | 15.0 | 10.9 | 3.96 | |
| 1940 | 15,811,000 |
| Average population | Marriages | Divorces | Crude marriage rate (per 1000) | Crude divorce rate (per 1000) | Divorces per 1000 marriages | ||
|---|---|---|---|---|---|---|---|
| 1919 | 11,706,957 | 225,605 | 19.3 | ||||
| 1920 | 11,881,764 | 185,954 | 5,687 | 15.7 | 0.5 | 30.6 | |
| 1921 | 12,059,178 | 157,055 | 6,720 | 13.0 | 0.6 | 42.8 | |
| 1922 | 12,239,245 | 131,776 | 6,548 | 10.8 | 0.5 | 49.7 | |
| 1923 | 12,421,997 | 129,796 | 6,492 | 10.4 | 0.5 | 50.0 | |
| 1924 | 12,607,480 | 114,896 | 5,508 | 9.1 | 0.4 | 47.9 | |
| 1925 | 12,795,732 | 123,005 | 5,481 | 9.6 | 0.4 | 44.6 | |
| 1926 | 12,986,796 | 124,249 | 4,940 | 9.6 | 0.4 | 39.8 | |
| 1927 | 13,180,709 | 124,104 | 5,254 | 9.4 | 0.4 | 42.3 | |
| 1928 | 13,377,523 | 121,334 | 5,580 | 9.1 | 0.4 | 46.0 | |
| 1929 | 13,577,272 | 128,120 | 6,070 | 9.4 | 0.4 | 47.4 | |
| 1930 | 13,780,006 | 138,322 | 5,826 | 10.0 | 0.4 | 42.1 | |
| 1931 | 13,982,000 | 126,072 | 6,393 | 9.0 | 0.5 | 50.7 | |
| 1932 | 14,174,000 | 111,059 | 5,231 | 7.8 | 0.4 | 47.1 | |
| 1933 | 14,369,000 | 111,503 | 5,500 | 7.8 | 0.4 | 49.3 | |
| 1934 | 14,566,000 | 99,704 | 5,520 | 6.8 | 0.4 | 55.4 | |
| 1935 | 14,767,000 | 110,129 | 5,561 | 7.5 | 0.4 | 50.5 | |
| 1936 | 14,970,000 | 109,528 | 5,022 | 7.3 | 0.3 | 45.9 | |
| 1937 | 15,172,000 | 117,717 | 6,547 | 7.8 | 0.4 | 55.6 | |
| 1938 | 15,384,000 | 121,605 | 6,466 | 7.9 | 0.4 | 53.2 | |
| 1939 | 15,596,000 | 123,817 | 7,103 | 7.9 | 0.5 | 57.4 | |
| 1940 | 15,811,000 |
The following data, grouped by first language, is from the 1921 population census:
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.