At the start of the twenty-first century, Europe has a population aging at an unprecedented rate. It is estimated that by 2050, 40% of Europeans will be over the age of 60. This problem is especially acute in the East whereas in the West, it is alleviated by international immigration. In addition, an increasing number of children born in Europe has been to non-European parents. Because children of immigrants in Europe tend to be about as religious as they are, this could slow the decline of religion (or the growth of secularism) in the continent as the twenty-first century progresses. In the United Kingdom, the number of foreign-born residents stood at 6% of the population in 1991. Immigration subsequently surged and has not fallen since (as of 2018). Researches by the demographers and political scientists Eric Kaufmann, Roger Eatwell, and Matthew Goodwin suggest that such a fast ethno-demographic change is one of the key reasons behind public backlash in the form of nationalist populist revolts against the political establishment across the rich liberal democracies, an example of which being the Brexit Referendum in 2016.