from total decline. Infrastructure and businesses along the border benefited from substantial state investment. East Germany's communities had a much harder time because the country was poorer and their government imposed severe restrictions on them. The border region was progressively depopulated through the clearance of numerous villages and the forced relocation of their inhabitants. Border towns suffered draconian building restrictions: inhabitants were forbidden from building new houses and even repairing existing buildings, causing infrastructure to fall into severe decay. The state did little but to provide a 15% income supplement to those living in the Sperrzone and Schutzstreifen; but this did not halt the shrinkage of the border population as younger people moved elsewhere to find employment and better living conditions. The GDR bore a huge economic cost for its creation of the border zone and the building and maintenance of its fortifications. The zone consumed around – more than six per cent of the East's territory, within which economic activity was severely curtailed or ceased entirely. The actual cost of the border system was a closely guarded secret, and even today it is uncertain exactly how much it cost to build and maintain. The BT-9 watchtowers each cost around 65,000 East German marks to build and the expanded metal fences cost around 151,800 marks per kilometre. The implementation of the "modern frontier" in the 1970s led to a major increase in personnel costs. Total annual expenditure on GDR border troops rose from 600 million marks per annum in 1970 to nearly 1 billion by 1983. In early 1989, East German economists calculated that each arrest cost the equivalent of 2.1 million marks, three times the average "value" to the state of each working person. Views of the border The two German governments promoted very different views of the border. The GDR saw it as the international frontier of a sovereign state – a defensive rampart against Western aggression. In Grenzer ("Border Guard"), a 1981 East German Army propaganda film, NATO and West German troops and tanks were depicted as ruthless militarists advancing towards East Germany. Border troops interviewed in the film described what they saw as the rightfulness of their cause and the threat of Western agents, spies and provocateurs. Their colleagues killed on the border were hailed as heroes and schoolchildren in East Berlin were depicted saluting their memorial. However, West German propaganda leaflets referred to the border