Political scientists have observed that the ideologies of political parties can be mapped along a single left–right axis. Klaus von Beyme categorized European parties into nine families, which described most parties. Beyme was able to arrange seven of them from left to right: communist, socialist, green, liberal, Christian democratic, conservative and right-wing extremist. The position of agrarian and regional/ethnic parties varied. A study conducted in the late 1980s on two bases, positions on ownership of the means of production and positions on social issues, confirmed this arrangement.