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Demographics

Yugoslavia had always been a home to a very diverse population, not only in terms of national affiliation, but also religious affiliation. Of the many religions, Islam, Roman Catholicism, Judaism, and Protestantism, as well as various Eastern Orthodox faiths, composed the religions of Yugoslavia, comprising over 40 in all. The religious demographics of Yugoslavia changed dramatically since World War II. A census taken in 1921 and later in 1948 show that 99% of the population appeared to be deeply involved with their religion and practices. With postwar government programs of modernisation and urbanisation, the percentage of religious believers took a dramatic plunge. Connections between religious belief and nationality posed a serious threat to the post-war Communist government's policies on national unity and state structure. Although Yugoslavia became a de facto atheist state, in contrast to other socialist states of the time, Catholic Church maintained an active role in society of Yugoslavia, the Holy See normalized its relations with Yugoslavia by 1967 and worked together on stopping the Vietnam War. Likewise, the Serbian Orthodox Church received favorable treatment, and Yugoslavia did not engage in anti-religious campaigns to the extent of other countries in the Eastern Bloc.

After the rise of communism, a survey taken in 1964 showed that just over 70% of the total population of Yugoslavia considered themselves to be religious believers. The places of highest religious concentration were that of Kosovo with 91% and Bosnia and Herzegovina with 83.8%. The places of lowest religious concentration were Slovenia 65.4%, Serbia with 63.7% and Croatia with 63.6%. The percentage of self-declared atheists was highest among Yugoslavs by nationality at 45%, followed by Serbs at 42%. Religious differences between Orthodox Serbs and Macedonians, Catholic Croats and Slovenes, and Muslim Bosniaks and Albanians alongside the rise of nationalism contributed to the collapse of Yugoslavia in 1991.

The Kingdom of Yugoslavia had unitary policies, suppressed autonomy and proclaimed the official ideology to be that Serbs, Croats, Bosniaks, Montenegrins, Macedonians and Slovenes were tribes of one nation of Yugoslavs (see Yugoslavism), to the heavy disagreement and resistance from Croats and other ethnic groups; this was interpreted as gradual Serbianization of Yugoslavia's non-Serb population. The ruling Communist Party of the Socialist Federal Republic of Yugoslavia was ideologically opposed to ethnic unitarism and royal hegemony, and instead promoted ethnic diversity and social Yugoslavism within the notion of " brotherhood and unity ", while organizing the country as a federation.