In 2006, the conservative Christian historian Philip Jenkins, in an article for the Foreign Policy Research Institute thinktank, wrote that by 2100, a Muslim population of about 25% of Europe's population was "probable"; Jenkins stated this figure did not take account growing birthrates amongst Europe's immigrant Christians, but did not give details of his metholodogy. in 2010, Eric Kaufmann, professor of politics at Birkbeck, University of London said that "In our projections for Western Europe by 2050 we are looking at a range of 10-15 per cent Muslim population for most of the high immigration countries – Germany, France, the UK"; he argued that Islam was expanding, not because of conversion to Islam, but primarily due to the religion's "pro-natal" orientation, where Muslims tend to have more children. Other analysts are skeptical about the accuracy of the claimed Muslim population growth, stating that because many European countries do not ask a person's religion on official forms or in censuses, it has been difficult to obtain accurate estimates, and arguing that there has been a decrease in Muslim fertility rates in Morocco, the Netherlands and Turkey.