A number of factors contributed to Portugal's poor agricultural performance. First, the level of investment in agriculture was traditionally very low. The number of tractors and the quantity of fertilizer used per unit area was one-third the European Community average in the mid-1980s. Second, farms in the north were small and fragmented; half of them were less than one hectare in size, and 86 percent less than five hectares. Third, the collective farms set up in the south after the 1974–75 expropriations due to the leftist military coup of 25 April 1974, proved incapable of modernizing, and their efficiency declined. Fourth, poor productivity was associated with the low level of education of farmers. Finally, distribution channels and economic infrastructure were inadequate in parts of the country. According to government estimates, about 9,000 km2 (2,200,000 acres) of agricultural land were occupied between April 1974 and December 1975 in the name of land reform; about 32% of the occupations were ruled illegal. In January 1976, the government pledged to restore the illegally occupied land to its owners, and in 1977, it promulgated the Land Reform Review Law. Restoration of illegally occupied land began in 1978.