It's a Wikipedia, I can't find it now...

There are all kinds of pressures...our history is rich (unfortunately).
http://www.country-data.com/cgi-bin/query/r-14804.html

Historically, the first cause of this scattering was the severe oppression of Serbs under Ottoman occupation, which led to migration to the unoccupied territory to the west. After World War II, Yugoslavia's first communist government tried to define the country's postwar federal units to limit the Serbian domination believed largely responsible for the political turmoil of the interwar period. This meant reducing Serbia proper to achieve political recognition of Macedonian and Montenegrin ethnic individuality and the mixed populations of Vojvodina, Kosovo, and Bosnia and Hercegovina (see Formation of the South Slav State , ch. 1).

Between 1948 and 1990, the Serbian share of Kosovo's population dropped from 23.6 percent to less than 10 percent, while the ethnic Albanian share increased in proportion because of a high birth rate and immigration from Albania. The demographic change was also the result of political and economic conditions; the postwar Serbian exodus from Kosovo accelerated in 1966 after ethnic Albanian communist leaders gained control of the province, and Kosovo remained the most poverty-stricken region of Yugoslavia in spite of huge government investments (see Kosovo , ch. 4; Regional Disparities , ch. 3). After reasserting political control over Kosovo in 1989, the Serbian government announced an ambitious program to resettle Serbs in Kosovo, but the plan attracted scant interest among Serbian émigrés from the region.

Science without religion is lame, religion without science is blind...Albert Einstein