Keywords

1 Introduction

It is usual for capital cities to undergo relatively rapid demographic change, whether in terms of absolute population, or age-specific population, compared to the rest of the country. Capital cities are usually the home of economic, social, educational, and cultural facilities, and therefore are poles of attraction for vital human capital (Harvey 1973, 1982). Another feature of major cities is that the socioeconomic compositions of their population can also evolve quite rapidly, as work opportunities make people migrate both on an international and national-regional scale, people of different social, ethnic, cultural and religious background. Since cities are the centers of change, they are also key actors in achieving social cohesion (Ranci 2011) as it is within cities that rapid increase of socio-economic and spatial disparities is most noticed (Cassiers and Kesteloot 2011).

Only a century ago, Vienna was one of the most populous cities of the world. Today, the Austrian capital is nowhere near the top in global urban population rankings; however it is still the second largest German-speaking city. After centuries of almost continuous growth, the population of Vienna peaked in the early 1900s, followed by nearly a century of decline and stagnation. Out of all European capital cities, only Vienna, together with Copenhagen, Berlin, and London were losing population between 1950 and 1975, and Budapest in the period from 1975 to 2010 (United Nations 2011). Contrasting with a stagnating absolute population of Vienna and surrounding areas – Vienna only grew by 7 % in 50 years between 1951 and 2001, from 1.45 to 1.55 million, yet its religious composition changed dramatically as more and more Christian inhabitants left the Church. Not until the late 1980s, Vienna’s population numbers started to rise again and recently increasing growth rates have made Vienna one of the strongest growing European citiesFootnote 1 during the first decade of the twenty-first century (Eurostat Database on Metropolitan regions)Footnote 2 which again had a large impact on the religious composition of the city.

Austria was in the past – as it still remains today – predominantly Roman Catholic, though several religious minorities, in particular Protestant and Jewish communities, have existed there for a number of centuries. Until recently, most changes in the religious landscape of Austria occurred through the enforcement of doctrines by the religious authorities, for example, the Counter-Reformation in the seventeenth century and/or by the political power in place, for example, the pogrom and holocaust of Jewish communities before and during the Second World War.

Since 1970 the homogeneity in terms of the domination in the population of one religious group, the Roman Catholic Church in the case of Austria, has been slowly fading away through two main forces: increased secularization and immigration of people belonging to other religions (Goujon et al. 2007). This transformation is quite unique in the history of religions but common to most “modern” societies. Moreover, migrant women, especially from Turkey, Serbia and Montenegro, and Macedonia have a higher number of children compared to native women, which is reinforcing the increase in religious pluralism due to migration. These phenomena lead to the diversification of the religious landscape in Austria and is exacerbated in the city of Vienna where both forces of secularization and migration are stronger than in any of the other Austrian federal provinces. Whereas from 1971 to 2001, the share of Roman Catholics decreased from 87 to 74 % in the whole country, it changed from 78 to 49 % in Vienna. During the same period, the share of those without religious affiliation rose from 4 to 12 % in Austria and from 10 to 26 % in Vienna. The share of the Muslim community, one of the fastest growing religions, rose from being close to 0 % in 1971 at the national as well as capital city level to 4 % in Austria and 8 % in Vienna in 2001. If half of the Muslims living in Vienna were born in Turkey, 30 % were actually born in Austria, and 18 % in former Yugoslavia. Vienna is home to 20 % of the Austrian population, but hosts a larger share of the population with a migratory background – 40 % – which makes 42 % of its population: 74 % of those are migrants of the first generation. The difference in the religious composition of the population between Vienna and the city of Austria is shown in Fig. 113.1.

Fig. 113.1
figure 1

Share of the population by religion and age in 2001 in Austria and Vienna (Source: A. Goujon and R. Bauer, data from 2001 population census, Statistics Austria)

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Side by side with the fading of church-related religiosity, individual beliefs such as the belief in God or self-assessed religiosity have weakened as well. During the last decade they have decreased most notably among young people and in rural areas (Zulehner and Polak 2009). Religious socialization in the family, an important precondition for future faith, is less common at present than 20 years ago. Baptism, a religious wedding and especially a religious funeral, on the other hand, remain widespread. When European countries are ranked by their level of religiosity, Austria is located at the lower end of the more religious half of countries, close to, for example, Switzerland or Slovenia (Voas 2009).

If secularization and international migration have been the main factors shaping Vienna’s changing religious landscape, more restrictive and selective migration as well as the resurgence of religion (Kaufmann 2010) may mean that the extent of fertility differentials by religious denominations and of exogamy could play the major roles in determining the future religious composition of Vienna.

Overall, the relative sizes of secular and religious populations belong to the most important social characteristics of any society. In the wake of religious change, family behavior, including marriage and childbearing, is likely to be altered. European demographic trends, including that of low fertility and progressively later childbearing are also likely to be affected when there is a growth of distinct religious groups with high fertility and with low rates of conversion and secularization. The changing religious distribution of the population can also have wider social and political ramifications, affecting the level of social cohesion, voting preferences, and potentially leading to an increase in segregation of specific minorities at a level of urban districts (Borooah 2004; Lehrer 2005; Morgan et al. 2002). One of the primary challenges for the Austrian government and the city council of Vienna will be to safeguard religious freedoms and to ensure a fair voice for foreign-origin populations and religious minorities including Muslims, while combating extremism, supporting the integration of minorities, and adapting European societies to diverse religious communities. At the city level, the changes in the distribution of the religious communities between the 23 districts of Vienna could have problematic implications in terms of segregation and ghettoization.

Most datasets on religion are based on surveys, and very few contain detailed information for the whole population, which make the Austrian and Vienna Census-based datasets unique,Footnote 3 as well as other register-based data on marriages, births, divorces, deaths, in- and out-flows (to the main religious denominations) that have been collected for many years by Austrian statistical authorities. On the other hand, census data, which include religious denomination but no information on the degree of religiosity, may conceal differences in religious intensity between religious groups. This chapter does not, however, address the issue of religiosity, but purely on the different religious denominations and their size and demographic behavior.

In our research within the framework of the WIREL projectFootnote 4 – WI for Wien/Vienna and REL for RELigion, that aims at addressing the role of religions in shaping the social and demographic structure of the population of Vienna, and their implications over a period ranging from 1951 to 2051. We investigate the changes that can be observed in the religious distribution of the population within Vienna and the different demographic forces that have been shaping this religious composition at the city level, namely, migration, differential fertility, and religious conversion. These findings will be used in the evaluation of the potential for the future evolution of these forces and the resulting religious landscape of Vienna until the middle of the century.

This chapter is divided into two main parts; the first section gives a brief history of the city of Vienna, the second shows the increasing religious diversity and in the third, we comment on the evolution of the different forces that were mainly shaping the city until now, namely migration and secularization, and the emerging demographic forces that will also be key to determine the future religious landscape, namely mixed unions and fertility.

2 A Short History About the Population of Vienna

Throughout history, cities always were bound to attract migrants and this kept their population numbers from falling, since the number of deaths generally exceeded the number of births (Flinn 1981). This was also the case in Vienna, but recurring wars and plagues kept the population from growing substantially until the late seventeenth century. After Vienna became the capital of the expanding Habsburg Empire and thus experienced more than two centuries of unprecedented urban population growth, almost entirely driven by immigration: from estimated 125,000 in 1700 (Weigl 2000a, b) to more than half a million by 1850, and up to two million in 1910. Natural population growth was generally negative until the second half of the eighteenth century and never exceeded the demographic gains achieved by migration, even after mortality rates dropped significantly in the course of the demographic transition during the second half of the nineteenth century (Weigl 2000a). During the period of strongest growth, between 1850 and 1910, more than half of Vienna’s population was born outside of the city. The many immigrants were not only attracted from the rural hinterland, but also – and in the wake of the Industrial Revolution (between 1830 and 1860 in Austria) predominately – from non-German-speaking parts of the multi-national Habsburg and Austro-Hungarian Empire: from Lombardy to Galicia and from Bohemia to Bosnia. By the turn of the twentieth century, Vienna was not only the fourth largest European city; it was also the second largest Czech city as well as the third largest Jewish city in Europe (Eppel 1996).

Vienna reached a peak population of 2.2 million in the aftermath of World War I, but found itself from now on as a capital of a small German-speaking country of 6.5 million, instead of being the administrative, economic and cultural center of a former multi-national Empire with more than 50 million people. Birth rates in Vienna tumbled down during war times and remained negative for the most part of the twentieth century. As accurately described by Weigl (2000a, b), between 1910 (just before World War I) and 1951 (when the first census after World War II was conducted), fertility rates strongly decreased far below the replacement level reaching absolute low-points during the Great Depression – the all-time low of 0.6 children per woman was achieved in 1934 (Lutz and Hanika 1989; Lutz et al. 2003). Some hundred thousand left Vienna in the years succeeding the war heading to the many successor states, but due to immigration from surrounding rural regions the population of Vienna stabilized during the 1920s and 1930s between 1.8 and 1.9 million. During World War II, Vienna lost almost its entire Jewish population of nearly 170,000 just before the war due to extensive expulsion in 1939 and the holocaust during the Nazi regime (Weigl 2000a). With more than 10 % of its population belonging to the Jewish denomination in 1923, Vienna was the third largest Jewish city in Europe (Lappin 1996). During World War II, the city’s population also suffered great losses among adult men at war service as well as among the civil residents during the final stage of the war. As a consequence, Vienna’s population decreased to merely 1.6 million after the end of the war and the city’s demographic structure was shaped by a skewed age – due to fertility and migration forces – and sex distribution caused by war casualties among men. In 1951, 13 % of the population was below age 15 and 20 % above the age of 60, and there were 1.2 women for each men living in Vienna.

As a result of these historical events and the associated demographic dynamics during the first half of the twentieth century, post-war Vienna was inhabited to some extent by a residual population: the former multi-cultural Vienna had become a distinctly heterogeneous city with respect to the ethnic and cultural background, as well as religious denomination of the population.

After the drastic population losses during World War II, Vienna’s population stabilized in numbers over the course of the 1950s and 1960s only because of considerable internal migration gains. International immigration remained on low levels, consisting mainly of refugee flows from neighboring socialist Eastern bloc countries: that is, Hungary in 1956, the former Czechoslovakia in 1968, and Poland in the early 1980s (Eppel 1996). However, the natural population balance still remained negative, even during the baby-boom years of the late 1950s and early 1960s. These demographic trends, in association with increases in life expectancy, turned Vienna into a city populated literally by old women. In 1971, more than a quarter of the population was above age 60, out of which two-thirds were women (Lutz and Hanika 1989).

The 1970s marked the reversal of several trends. First of all, internal migration became negative as more people moved to the suburbs of Vienna, and international migration increased substantially as a political effort to counteract the persistent shortage of labor with the recruitment of workers mainly from Yugoslavia and Turkey, the so-called Gastarbeiter (guestworkers). If the combination of both trends led the city to still lose about 5 % of its population between 1971 and 1981, it also triggered a process of (re-)diversification and rejuvenation in the long run. After 1971, the share of the elderly population gradually decreased and the share of the foreign-born population increased. The Gastarbeiter did not return home as originally intended, but rather brought their families in order to settle in the long-term, while more workers and their families followed their trails (Fassmann and Münz 1995).

In 1988, population numbers reached a low point of 1.48 million. After the fall of the Iron Curtain, Vienna became an attractive destination again for immigration from the neighboring Central European countries, and from Yugoslavia during the early 1990s, especially in the course of the Bosnian War. In 1995, Austria became member of the European Union, and Vienna started attracting as well EU citizens, especially from Germany. During the 1990s, international migration became the undisputed driver of Vienna’s regained population growth. The 2001 census count for Vienna was 1.55 million and 1.71 million in 2011: a 10 % increase, the result of the persistent inflow of international immigrants and natural increases. Beyond that, the accelerated globalization established new migration regimes and further diversified the geographic origins of the new immigrants and, hence, also stimulated the ethnical, cultural and religious heterogeneity of today’s population of Vienna. A research team at the University of Vienna is in the process of investigating the 800 or more places of cult in the city that have until now not been systematically enumerated.Footnote 5

3 Increasing Religious Diversity

In 1951, the religious landscape of Vienna was characterized by the dominance of the Roman Catholic Church. About 82 % of the population were Catholics and, adding the 8 % Protestants as well as a few members of Eastern Orthodox Churches, more than 90 % of Vienna’s population was Christian by denomination. The rest of the population split up between 2 % with other religions – including a small Jewish community that survived the Shoa and stayed in Vienna – and a considerable share of up to 8 % without any religious denomination. This relatively high share of people without religion in 1951, compared to the rest of Austria, and to presumably other European cities at the same time, find roots in the strong social-democratic tradition in Vienna (das “Rote Wien”), which goes back to the late nineteenth century and was predominately anti-clerical orientated – and also anti-Semitic to some extent.

Figure 113.2 shows that the religious distribution remained stable over the course of the 1950s and 1960s, although Catholics lost a few percentage points, while the share of secular people with no religious denomination increased slightly. Some other small shifts are visible – the share of Orthodox (included in “other” in the figure) and Muslims slightly increased and a Muslim community re-emerged since the arrival of the first Gastarbeiter from Yugoslavia and Turkey in the late 1950s. The 1971 census clearly revealed that Vienna was still a largely Catholic city: almost four out of five professed to be Roman Catholic.

Fig. 113.2
figure 2

Increasing religious diversity in Vienna, 1951–2007 (Source: A. Goujon and R. Bauer, data from Statistics Austria censuses for 1951–2001; estimates for 2007 from Goujon et al. 2007)

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Between the 1971 and the 2001 census – when religious denominations were surveyed for the last time3 – the previously rather homogeneous religious landscape of Vienna became considerably more diverse. By 2001, Catholics became a minority in Vienna (49.2 %), while the secularized population without any religious denomination strongly increased (from 10.5 % in 1971 to 29.5 %) and is about to become the strongest group (37 % in 2007 versus 42.6 % Catholics – see also Fig. 113.2). Like the Catholics, also the share of Protestants decreased by more than a third during the last three decades of the twentieth century (from 6.9 to 4.7 %). Besides those major shifts, the share of Muslims increased from less than a half per cent in 1971 (0.4 %) to nearly 8 % (7.8 %) and, hence, already outnumbered the city’s Orthodox population (6 %). All in all, the 2001 census distinguished between 47 different religious denominations, including some established religions like Jews and Old Catholics (around 0.45 % each) and many previously unseen or unrepresented religions like Buddhism (0.3 %), Hinduism and Sikhism (both together 0.27 %) and also Mormonism and Baha’ism (both below 0.1 %) among others. At the turn of the millennium, Vienna had truly become a city of religious diversity.

Figure 113.3 shows the spatial dimension of Vienna’s religious diversity in 2001 at the neighborhood level. The map is based on the share of the largest religious group (usually Catholic), that is, the smaller the share of the largest group, the more diverse is the neighborhood. Hence neighborhood diversity is assessing the mix of various groups rather than the concentration of one particular group, In Vienna, the most diverse neighborhoods are clustered along a heavy traffic ring street called “Gürtel” (German for “belt”), which surrounds the inner more urban districts and separates them from the outer ones. On one hand, these areas are characterized by high shares and hence concentration of ethnic minorities with a higher prevalence of migrant minority religions such as Islamic and Orthodox denominations; on the other hand, some of these areas are rather gentrified neighborhoods with a high share of secular population.

Fig. 113.3
figure 3

Neighborhood diversity by religion in Vienna, 2001 (Map by A. Goujon and R. Bauer with data from 2001 population census 2001, Statistics Austria)

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4 Demographic Drivers of Religious Change

4.1 Religious Mobility

One particularity of Austria is that members of the Catholic and Protestant Church have to pay a yearly fee directly to the Church – 1.1 % of the net pre-tax income of Catholic members and 1.5 % of the self-reported income of Protestants.Footnote 6 Hence religious mobility in terms of exit and entrance to the Christian churches are well known, and are shown in Fig. 113.4. Overall since the 1960s, the Catholic and Protestant Churches have been losing members, in a similar pattern but at a different scale, with less and less compensation coming from new entrants – data on entrance are only available until 1984). The period 1979–1983 was a time of major losses for the Catholic Church in Vienna and it peaked in 1983 with 17,000 members cancelling their Church membership – a record until now. Since then, the trend in terms of losses has been reversed, with clearly less exits by the year, but also more erratic patterns with peaks every now and then. Most of the peak losses (1995, 1999, 2004, and 2010) for the Catholic Church correspond to church-related sexual abuse scandals in Austrian Catholic Institutions (schools or Boy’s choir) or elsewhere, notably in Belgium, Netherlands, Germany, and Ireland. Beyond the acts of child abuse themselves, the opinion in Austria was particularly scandalized by the attempt of the Church to cover up the stories, like in the case of the Archbishop of Vienna, Cardinal H.H. Groer, against whom charges of sexual misconduct were pronounced in 1995, but were ignored by the Church hierarchy until early 1998 when a papal investigation finally commenced. Finally a few months later, Cardinal Groer had to relinquish all ecclesiastical duties and privileges.

Fig. 113.4
figure 4

Religious mobility in Vienna, 1950–2010 (Source: A. Goujon and R. Bauer, data from City of Vienna Statistical Yearbooks 1950–2011)

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Although at first sight, the Protestant Church, which consists only of the Evangelical Church of the Augsburg and Helvetic Confessions (often abbreviated as Evangelical AB and HB) – other Protestant confessions are not counted under this group–, seems to be experiencing the same history of membership exits as the Catholic one, the Protestant pattern is different in three ways. First of all, the Protestants were able to compensate the loss of members through the entrance of new members much more than the Catholics. For instance in 1963, for one new member in the Catholic Church, there were three exiting members (1:3), whereas for the Protestants, the ratio was two to 3 (2:3). The difference between the two Churches in terms of gains and losses diminished over time. The second difference is that the Protestant Church is much less affected by the scandals than the Catholic one, and is, therefore, experiencing less membership fluctuations. Finally, and this is obvious looking at Fig. 113.5, whereas there is more mobility among the Catholic men, at least until the beginning of the twenty-first century, for the Protestants, and with a few exceptions, the majority of quitters are women. In former times, women have always been the ones in charge of religions in families, responsible for religious feelings, religious education, and religious practice, which would explain the higher retention for women among the Catholic Church. However, Protestant women in the 1950s–1970s, who were often marrying outside of their religion, mostly a Catholic husband, were more prone to change their religion in obedience to their spouse. Within the last few decades women started to look for new ways of religious experience, mostly in order to revitalize religion inside and outside of Churches, which would explain the stronger mobility in the most recent periods as well as the fact that women became more independent. For the other religions where data are available (old Catholic, Jewish, and other Christian denominations), there are also more women than men among the religiously mobile population which would confirm the minority hypothesis.

Fig. 113.5
figure 5

Share of women in religious mobility in Vienna, 1950–2011 (Source: A. Goujon and R. Bauer, data from City of Vienna Statistical Yearbooks 1950–2011)

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Trends in the age at which the members decide to leave the Church bring interesting information. Most of the transitions occur before the age of 60, with a peak around the age of 21–40. However the occurrence of the peak seems to differ greatly according to the decades of observations with no recognizable patterns, especially the 1960s are exhibiting some strange patterns potentially due to the absence of data for the years around 1968. Unfortunately, the age breakdown is not available after 1983.

4.2 International Migration Flows by Religion, Vienna (1992–2010)

Although very detailed data are available on religion in Vienna and the rest of Austria, very little is known about the religious denomination in migrant flows, meaning of the immigrants to, and emigrants from Austria. These data have to be imputed using the random migration hypothesis – meaning that migrants are assumed to have the same religion as the population in the country of origin. Although this is a strong assumption to make, and can be detrimental to the analysis for some particular religious groups in some particular years, this method has been shown to lead to quite reasonable estimates of the religious distribution of the migrants (see Goujon et al. 2012; Skirbekk et al. 2010). What is clearly visible from Fig. 113.6 is that immigration to Vienna was very high at the beginning of the 1990s, after the breakup of Yugoslavia. At that time, three-quarters of the international migrants to Vienna were Muslims from Turkey and Former Yugoslavia. In the early 2000s, following the entry of Austria in the European Union in 1995, international immigration to Vienna was equally high, but the share of Muslims has declined and recent migration flows are equally driven by the Catholic-, other- (mostly Orthodox) and Muslim-denominations. In 2011, the ten top countries in terms of net-migration to Vienna were Slovakia, Bulgaria, Turkey, Russia, Bosnia and Herzegovina, Afghanistan, Italy, Serbia (incl. Montenegro and Kosovo), Ukraine, and India. Migration is noticeably acting as a counterweight to secularization in the native population as the share of the population without religion seems to be lower as in the total population. However little is known about the secularization behavior of those immigrants to Austria.

Fig. 113.6
figure 6

International migration flows by religion, Vienna 1992–2010 (Note: migration flows of Austrian citizens are not included) (Source: A. Goujon and R. Bauer, data from City of Vienna Statistical Yearbooks 1993–2011)

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If the religious status of migrants (flows) is not reported, more can be said about the foreign born population in Vienna (stock), based on censuses. In 2001, the foreign born population residing in Vienna was approximately shared between Roman Catholics (24 %), Muslims (23 %), Orthodox (19 %) and those without religion (20 %). As can be seen from Fig. 113.7 the largest group of foreign born population in Vienna, originated from Former Yugoslavia (particularly Serbia and Montenegro, and Bosnia and Herzegovina).

Fig. 113.7
figure 7

Population by religion and country of birth (excluding Austrian citizens) in Vienna, 2001 (Source: 2001 population census 2001, Statistics Austria)

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5 Total Fertility Rates by Religion, Vienna (1971–2010)

The fertility in Vienna has been overwhelmingly stable during the last 40 years as can be seen from Fig. 113.8, oscillating between 1.3 and 1.5, and actually most women in different religious denominations are having low and stable fertility behavior, between 1.2 and 1.5 – that is at least the case of the two main Christian denominations: the Catholics and the Protestants. Although the data on the Orthodox population only became available at the time of the 2001 census, it seems that this group is also following low patterns of fertility (with a TFR estimated at 1.35 in 2001). Two groups stand out: the Jewish, dominated by Orthodox Jews in Vienna, and the Muslims whose fertility started very high in the 1980s (3.9) as a result mostly of family reunification and changing countries of origin in the early 1990s and was around 2.8 in 2001. Further estimates of fertility by scholars (in Saunders 2012) point at further declines in Muslim fertility as Austria’s Muslims had a recorded fertility rate of 3.09 children per mother in 1981, 2.77 in 1991, and 2.3 in 2001 (see also Goujon et al. 2007).

Fig. 113.8
figure 8

Total fertility rates according to the religion of mothers in Vienna, 1971–2010 (Note: estimates at census years are based on the total population, the female population in childbearing ages, and the general fertility rate) (Source: A. Goujon and R. Bauer, data from census 1971–2011, Statistics Austria and City of Vienna Statistical Yearbooks 1972–2010)

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The decline in Muslim fertility, evident from birth records shown in Table 113.1, both in Vienna and in Austria is due to two phenomena. First of all, migration from Muslim countries is diminishing and hence the weight of second generation migrants converging to native (Austrian) low fertility patters in the overall Muslim population becomes more important. Secondly, in the main countries of origin of Muslim migrants, the fertility is experiencing strong declines – In Turkey, the total fertility is below the replacement level of 2.1, where as it was above 4 in the 1970s.

Table 113.1 Births to Muslim women, by country of origin, 2008–2011
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6 Marriages and Divorces Within Religions, Vienna 1950–2008

Catholics, especially men still marry in majority inside their religion whereas Protestants, in minority, tend to marry outside (Fig. 113.9). Both sexes in both religions tend to marry less and less inside their own religion. The trend is rather the opposite for Muslims and Orthodox. For Muslims, exogamy is rather typical of men whose wife will most likely convert to Islam. The transmission of religion from parents to children of those children born to mixed marriages will become increasingly important. Lutz and Uljas-Lutz (1998) estimated that only half of the children born to mixed couples with one spouse being Protestant became Protestant. Lutz (1985) shows that the religion of the mother is more important than the religion of the father for the transmission of religion from parents to children.

Fig. 113.9
figure 9

Marriages within religions, Vienna 1950–2008 (Source: A. Goujon and R. Bauer, data from City of Vienna Statistical Yearbooks 1950–2011)

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Not unrelated to the different patterns of mixed marriages across religions are those of divorces between sexes, which show that the majority of divorces among Catholics and Protestants were attributed to men, until 1985 when data were available, whereas there were more divorces among married women partners with other religions and/or no religion than among their male counterparts that could be due to the fact that these women had a higher status – mostly educational and financial – than the Catholic and Protestant women which allowed them more freedom to move out of a union.

7 Conclusions and Outlook

Vienna, a city that was distinctly homogenous in terms of population composition in the mid-twentieth century, became a city of ethnic, cultural and religious diversity. This can be studied demographically as all changes related to changes in the composition of the religious landscape of the city of Vienna are related to demographic events: migration and fertility. Other drivers of change such as secularization or religious mobility express also a form of migration from one religious status to another. We have shown in this chapter that secularization and international migration have been the main factors shaping Vienna’s changing religious landscape, as this was the case in most countries in Europe, and North America. More restrictive and selective migration as well as the resurgence of religion (Kaufmann 2010) may mean that the extent of fertility differentials by religious denominations and of exogamy could play the major roles in determining the future religious composition of Vienna. The WIREL project will further evaluate the potential of future pathways of these forces and the resulting religious landscape of Vienna until the mid-twenty-first century.