There has been a wealth of research on the "return of religion" versus "secularization in Europe" in recent decades. For quite a while, there have been marked debates on the question of old versus new forms of religion and especially on the phenomenon of “believing without belonging”. Although, this did not provoke substantial efforts to answer the question of religious belonging empirically.
Religious affiliation has not been at the forefront of scientific research on religion. Although some scientists realized the problem of poor statistics on religious affiliation across Europe, scholars have more often followed a strategy of giving specific numbers without debating data problems in depth. However, there were no official data on religious affiliation in EU statistics or those from other international organizations. On the other hand, almost all international social-science survey programs such as the World Value Survey, European Value Study, or International Social Survey Programme feature some questions on religious belonging and come up with data.
In 2010 the endeavor that has now become the SMRE project started with the surprising discovery that even the most recent scientific literature differs substantially on figures on religious affiliation in Europe (for more details and evidence see Liedhegener / Odermatt 2013).
Based on social science standards there is actually a need to provide more reliable statistics on the religious composition of Europe.