Since the terror attacks on September 11, 2001, there has been a massively growing interest in Muslims living in the West. The German book market in particular is overflowing with more or less competent publications on the theme. Facts, however, are hard to come by as most official statistics are based on a census that does not register religion. As for Muslims, their number is mostly estimated on the basis of the Muslim share of the population of the immigrants' home countries. A few studies, however, have targeted the opinions of Muslims, their socio-economic status and other relevant parameters.
According to the most recent study by the Federal Ministry of the Interior, which came out in 2009, approximately 4.3 million Muslims live in Germany corresponding to 5.2 percent of the total population. 45 percent of them have German citizenship. On the basis of German statistics, the American Pew Research Center estimates that by the beginning of 2011, Germany's Muslim population was approximately 4.1 million (5 percent of the total population). The number of Muslims is estimated to increase to approximately 5.55 million by 2030, corresponding to 7 percent of Germany's total population. Most of the increase is due to a higher Muslim birth rate. Over the period 2005-2010, the average Muslim birth rate was 1.8 children per woman, whereas it was only 1.3 percent among non-Muslim woman. Over the next 20 years, the Muslim birth rate is predicted to decrease slightly to 1.7 children per woman.