This prosperity was achieved despite severe restrictions placed on the city's economy by central government, which explicitly sought to limit Birmingham's growth. The Distribution of Industry Act 1945 prohibited all industrial development over a specific size without an "Industrial Development Certificate", in the hope that companies refused permission to expand in London or Birmingham would move instead to one of the struggling cities of the North of England. At least 39,000 jobs were directly transferred out of the West Midlands by factory movement between 1960 and 1974, and planning measures were instrumental in local firms such as the British Motor Corporation and Fisher and Ludlow expanding in South Wales, Scotland and Merseyside instead of Birmingham. Government measures also acted indirectly to deter economic development within the city: restrictions on the city's physical growth in an era of economic boom led to extremely high land prices and shortages of premises and development sites, and moves to reduce the city's population led to labour shortages and escalating wages.