The countries of western Europe possess a substantial number of what are commonly described as think tanks. In western Europe, the definitional blurring necessarily increases as one moves across the continent from north to south. A few think tanks were also set up by trade union federations and employers' organizations, although such initiatives have been untypical in western Europe. Western Europe's many party-linked think tanks are a different category, in that they are obviously not wholly independent nor nonpartisan. The most important source of income for think tanks in western Europe overall is the state, at national or regional government level. The second most important source overall—although the proportion is difficult to quantify—is probably the European Union, of which fifteen of the twenty countries covered are members. Another important think tank characteristic in western Europe, cutting across at least three of the typologies, is that many of them have memberships in addition to their professional staffs.