After the Cuban revolution and before the collapse of the Soviet Union, Cuba depended on Moscow for substantial aid and sheltered markets for its exports. The loss of these subsidies sent the Cuban economy into a rapid depression known in Cuba as the Special Period. Cuba took limited free-market oriented measures to alleviate severe shortages of food, consumer goods, and services. These steps included allowing some self-employment in certain retail and light manufacturing sectors, the legalization of the use of the US dollar in business, and the encouragement of tourism. Cuba has developed a unique urban farm system called  to compensate for the end of food imports from the Soviet Union. The U.S. embargo against Cuba was instituted in response to nationalization of U.S.-citizen-held property and was maintained at the premise of perceived human rights violations. It is widely viewed that the embargo hurt the Cuban economy. In 2009, the Cuban Government estimated this loss at $685 million annually.