The shortage of foreign exchange because of a chronic trade deficit, a large foreign debt, and dwindling foreign aid has constrained economic development. In addition, North Korea has been diverting scarce resources from developmental projects to defence; it spent more than 20% of GNP on defence toward the end of the 1980s, a proportion among the highest in the world. These negative factors, compounded by the declining efficiency of the central planning system and the failure to modernize the economy, have slowed the pace of growth since the 1960s. The demise of the communist regimes in the Soviet Union and East European countries—North Korea's traditional trade partners and benefactors—has compounded the economic difficulties in the early 1990s.