 Complete the following phrase:  At the start of the twenty-first century, Europe suffers from an aging population. This problem is especially acute in Eastern Europe, whereas in Western Europe, it is alleviated by international immigration. Researches by the demographers and political scientists Eric Kaufmann, Roger Eatwell, and Matthew Goodwin suggest that such immigration-induced ethno-demographic change is one of the key reasons behind public backlash in the form of national populism across the rich liberal democracies, an example of which is the 