Kosovo at the time of the too-mythologized 1389 Battle of the Black Birds was the heartland of the Serbian state and likely Serb in population. This began to change in the 15th century, as Serbs migrated northwards into the Kingdom of Hungary, many settling in the lands which now make up Vojvodina. At the same time, the population mixtures of many Balkan regions began to change thanks to what John Allcock in Explaining Yugoslavia describes as "metanastasis", the spontaneous movement by semi-nomadic families from poorer lands to richer ones. By the 18th century, Albanians seem to have had a growing presence in Kosovo.
Towards the end of the Ottoman era, the Albanian proportion of the population seems to have risen sharply. Statistics on the ethnic balance in Kosovo at this time are uncertain, not only because of the influence of various nationalisms but because Ottoman censuses recorded only the religion of their subjects not their nationality. Various sources do suggest that perhaps as much as two-thirds of the population of the region that makes up Kosovo was Albanians by the beginning of the 20th century. Tim Judah (Kosovo: War and Revenge</i>) sums up the overall situation by noting that "much of the southern and western parts of Kosovo were thoroughly Albanian" but "that other parts had compact Serbian populations, especially in the east and from Mitrovica to the then Serbian border" (15). This general portrait, however, was complicated by the massive population movements, as Albanians and other Muslims streamed south and Serbs streamed north into the new Kingdom of Serbia.
Afterwards, the history of Kosovo in the first half of the 20th century was marked mainly by acts of genocide conducted against one civilian population or another. Leon Trotsky witnessed mass killings of Albanians and other Muslims by Serb forces in the First Balkan War, followed by Albanian reprisals against Serb forces and civilians during the First World War, followed by Serbian-cum-Yugoslav reprisals in the 1920s and an ongoing colonization campaign and emigration of Albanians (at least one hundred thiosand emigrants from 1910 on) , followed by Italian invasion and wholesale massacres conducted mostly by Italian-backed Albanians against various Serb populations, followed by a reconquest of Kosovo by Tito's partisans and, finally, Kosovo's annexation to Serbia as an autonomous province.
Curiously, all these atrocities had little effect on the ethnic balance in the region, perhaps because they counterbalanced each other, and two-thirds of Kosovo's population remained Albanian.
Outsiders observed at least as early as 1967 that Kosovar Albanians' population was growing very quickly (%3.2 per annum in 1967). Marina Blegojevac's essay in The Road to War in Serbia suggests that Kosovar Albanian conservatism in relation to gender roles played a major role in the delayed demographic transition, but the isolation of the Albanians in a sea of speakers of various Slav languages may also have insulated them, as might have continued survival of a peasant agricultural economy long after industrialization had transformed the rest of Yugoslavia. (It's worth noting that birth ratesKosovo and western Bosnia Serbs, both backward areas, seem to have been high relative to those of Serbs in central Serbia, although not nearly as high as that of Kosovar Albanians.) The assessment of Noel Malcolm (Kosovo: A Short History) can be taken as authoritative.
The Albanians of Kosovo do have a very high birth-rate: the highest, in fact, in present-day Eutrope. They are still a mainly agricultural scoiety, and life in the villages is strongly traditional; the tradition of large families developed through many centuries as a response to the death-toll of disease and blood-feuds in the one hand, and general conditions of insecurity on the other. What has happened in the twentieth century is that mortality (from feuds, infectious diseases and perinatal problems) has been qutie sharply reduced, while the tradition of large families has been eroded much more slowly. In the post-war years the Albanian birth-rate in Kosovo has come down from forty-six births per 1,000 head of population in the early 1950s to roughly twenty-nine in the late 1980s. What these overall figures conceal, however, is that birth-rates vary among the Albanians, as among any modern population, in accordance with the socio-economic status of the mother: in 1981 rural housewives would have on average 6.7 children, but urban working women only 2.7. The idea that Albanians breed as part of a political campaign is rather neatly disproved by this evidence, since the urban couples are much more likely to be politicized than their counterparts in remote villages.
One other element of the statistical evidence which is often overlooked is that all ethnic groups in Kosovo have relatively high birth-rates; the 1981 census showed that a Serb woman in Kosovo would have on average 3.4 childrnen by the end of her child-bearing years, while her equivalent in inner Serbia would have only 1.9. In these matters, as in many others, the Serb population in Kosovo had a traditional way of life quitesimilar to that of its Albanian neighbours. In the early 1950s the Serbs had a birth-rate almost as high as the albanians (forty-one per 1,000), and since their mortality rate was much lower, their net rate of population growth was actually greater (2.7 per cent growth per year, as opposed to the Albanians' 2.1) (332-333).
A comparison of the 1971 and 1981 Yugoslav censuses revealed the changing ethnic balances of the Yugoslavian population: There were slight declines in the populations of Croats and Serbs, slight growth among Slovenes, relatively more rapid growth among Muslims by nationality and Montenegrins, and very rapid growth in the numbers of self-identified Yugoslavs and Albanians, that last population growing from 1.3 to 1.7 million. More germanely, the population density of Kosovo was twice that of Serbia proper, Vojvodina, or Serbia, and unlike those areas Kosovo's population was continuing to grow quickly. As early as 1972, Kosovar Albanians were arguing that the sharp growth in the Kosovar Albanian population strengthened the case for Albanian recognition as a fully-fledged Yugoslav nation and the transformation of an increasingly autonomous Kosovo into a full-fledged republic of Yugoslavia.
It's at this sensitive point that the world economic crisis hit, and Yugoslavia's generally high-income but import-dependent economy came under heavy pressure. The richer areas, like Slovenia and Croatia, did better than the poorer areas. The worst off was Kosovo, already underdeveloped and transferred massive amounts of development funds from the rest of Yugoslavia which failed to make a dent in a worsening economic situation. Robert Thomas' The Politics of Serbia in 1990s (reviewed here), the Kosovar economy was doing badly by the 1980s due to a combination of poor organization, low wages, and very low productivity, The lead and zinc mines of the Trepca mining complex were facing huge losses while the grossly inefficient Ferronikl plant was operating only at 70% of capacity in 1987, and even agriculture was in decline. This stark economic situation wasn't helped by rapid population growth--the efforts of Kosovo's leadership were too late to avert continued rapid growth in the labour force, and, not incidentally, ethnic tensions.
Even before the Second World War, Kosovo tended to be a producer of migrants, not only voluntary emigrants but involuntary ones. The wholesale forced migration of Kosovar Albanians had been discussed by historian Vaso Cubrilovic, who in his 1937 essay "The Expulsions of the Arnauts" argued in favour of mass expulsions to Albania: "At a time when Germany can expel tens of thousands of Jews and Russia can shfit milluions of people from one part of the continent to another, the shifting of a few Albanians will not lead to the outbreak of a world war." (23)
Later, the numbers of migrants and their directions became still more complex. Tim Judah's attempt to parse the dynamics of the various population movements is probably the best that can be hoped for.
According to the census returns, the number of Serbs and Montenegrins in Kosovo remained relatively stable, moving between 200,000 and 260,000 in the post-war period. What does change though is that their numbers, as a proportion of the total</i>, dropped from a combined 27.5 per cent in 1948 to 14.9 per cent in 1981 and 10/9 per cent in 1991. This was not just due to Serb emigration, which in turn contributed to the lack of the natural growth of the population, but to the fact that the Albanian birth-rate was extremely high. [. . .]
Not only is it difficult to work out exactly how many Serbs were really leaving but it is also difficult to work out why they were leaving. During the 1970s and 1980s Kosovo's administration, and just about everything else in the province, was progressively Albanianised. This meant that the Serbs lost their privileged status in the administration and state sector. One reason for this was that Pristina University was producing thousands more graduates than the economy could possibly absorb. Family and other contacts inevitably meant that they would get jobs before Serbs. This in turn meant that young families tended to leave for Serbia proper because there were jobs in the factories of central Serbia and besides, there was no hassle there about being a Serb. But whether the majority of people left becase they were discriminated against, felt threatened or simply felt that they or their children had no future in an Albanian-dominated Kosovo is a moot point. Probably the push factors were a combination of all of these, despite what propagandists of either side would like to pretend.
[. . .]
The other side of this quarrel was one over the numbers of Albanians who had emigrated to Turkey in the post-war years, during the Rankovic era when Serbs dominated life in Kosovo. Was this a form, as Albanians later charged, of what we now call ethnic cleansing or the willing emigration of people who want to live with family already there or simply did not want to live in a Communist country. Between 1952 and 1967, 175,000 Muslims emigrated from Yugoslavia to Turkey, but exactly how many of these were Albanians (probably a majority), as opposed to, say, Slavic Macedonian Muslims or ethnic Turks, is unclear (44-45)</i>
It doesn't help clarify things to observe, after Judah, that internal migration in Yugoslavia tended to orient itself along ethnic lines.
[E]ver since the war, there had been considerable demographic shifts across Yugoslavia. So, for example, peasants from poor areas of Montenegro and Bosnian and Croatian Serbs had moved in considerable numbers to the rich farmlands of Vojvodina and eastern Croatia where they were given homes and land which had belonged to the some 350,000 ethnic Germans who had been expelled, or fled, after the war. Industrialisation in Serbia and Croatia had also acted as a magnet for Bosnian Serbs and Croats respectively, and as mentioned, Serbs from Kosovo. Higher education was a pull factor too. Intelligent young Serbs would gravitate to Belgrade University, Croats to Zagreb and Muslims, from the Sandzak area of Serbia, which has a considerable Musl;im population, to Sarajevo. Few of them would ever return home because the jbos for skilled people were io the big cities. (44-45)
This is backed up by Malcolm.
In the Yugoslavia of the later Tito years, however, Serbs from Kosovo were not the only people engaging in internal migration. From the early 1960s onwards there was a large-scale flow from all the under-developed areas to the more developed or developing ones. Bosnia-Hercegovina, for example, the second poorest part of Yugoslavia after Kosovo, had suffered proportionately an even larger outflow of its population by 1981; understanably enough, this basically economic phenomenon also had a national colouring to it, with Bosnian Croats moving mainly to Croatia and Bosnian Serbs to Serbia. Inner Serrbia may not have been as prosperous as some other regions, such as Slovenia, but thanks to the expansion of Belgrade and the industrial development of Serbian cities such as Kragujevac it attracted a higher net immigration, from all parts of Yugoslavia, than any other area. In 1981 the population of inner Serbia included 111,828 people who had moved there from Bosnia, 110,704 from Croatia (mainly from poor Serb-inhabited rural areas), 50,011 from Macedonia, and so on (330).
Whatever the reason, newly intense competition over scarce economic resources like jobs and school positions aggravated by nationalist hostility between Albanians and Serbs. Things might not have deteriorated so badly if all Kosovars could have participated in the long-standing Yugoslavian tradition of heading to western Europe to work, but unfortunately the world economic recession had caused these countries to close their doors. Lacking the family and language connections of Yugoslavia's South Slavs, Kosovar Albanian long-range migration seems to have been directed mainly to central and northern Europe.
What was the net result of these trends? Albanians in Kosovo emerged as a demographically significant population, responsible for a disproportionately large share of the Republic of Serbia's births and an even larger share of its total natural increase. By the late 1980s, this fact, along with growing concern over the "white plague" of low or negative natural increase among Serbs, combined with growing nationalism on all sides and a considerable amount of ethnic to produce an unseemly mess of nationalist hysteria. Reproduction, sexuality, and gender all played major--and unanswerable--roles, as Mark Thompson described in A Paper House.
Facts were scarce amid the delierium, but were hardly the point. Truth was a necessary casualty of this mobilization, and its medium was myth. When one Djordje Martinovic claimed in 1985 that two Kosovars had raped him with a broken bottle, he became a national martyr, an archetype of Serb suffering and Albanian (Muslim, Ottoman ...) evil. A poetry likened him to the Serb rebels impaled by the Turks of old. In due course the courts and medical examiners agreed the man was unbalanced and his wounds were self-inflicted; but who cared?
A Croatian journalist investigated the many allegations that Serb and Montenegrin women were being raped in Kosovo. Records showed no disproportion among Albanian and Slav criminality in the province, and a lower than average number of rapes. Researchers in Belgrade bore the journalist out; but by the time their dull book of statistics was published in 1990, who cared?
If the official figures proved that hundreds of thousands of refugees had not crept over the border from Albania, and hundreds of thousands of Serbs and Montenegrins had not been scared into fleeing the province, who cared? There was no separatist movement of any substance, but who cared? The Kosovars' weary insistence that separatism was not the issue, only confirmed their perfidy (129-130).
Kosovar separatism soon became an issue, of course. The 1981 popular protests demanding Kosovo be made a republic, one of seven without the SFRY, didn't aim for secession from Yugoslavia. By the time that Yugoslavia was dissolving, the idea of Kosovo gaining independence from a threatening Serbia seemed like a good idea.