For example, a regional referendum in 1996 to merge the city Lander of Berlin with the surrounding Lander of Brandenburg as ‘"Berlin-Brandenburg” failed to reach the necessary majority vote in Brandenburg, while a majority of Berliners voted in favor of the merger (Hauswirth, Herrschel and Newman, 2003). Instead, the main mechanism is some form of voluntary agreement that results in co-ordinated actions (OECD, 2015). These agreements can be complex to negotiate and may be limited, at least initially, to topics where all parties see an immediate benefit.