Between 1975 and 1991, the MPLA implemented an economic and political system based on the principles of scientific socialism, incorporating central planning and a Marxist–Leninist one-party state. It embarked on an ambitious programme of nationalisation, and the domestic private sector was essentially abolished. Privately owned enterprises were nationalised and incorporated into a single umbrella of state-owned enterprises known as "Unidades Economicas Estatais" (UEE). Under the MPLA, Angola experienced a significant degree of modern industrialisation. However, corruption and graft also increased and public resources were either allocated inefficiently or simply embezzled by officials for personal enrichment. The ruling party survived an attempted coup d'état by the Maoist-oriented Communist Organisation of Angola (OCA) in 1977, which was suppressed after a series of bloody political purges left thousands of OCA supporters dead.