Angola's industries grew by an annual average rate of 17% in the 1960s as ethnic Europeans seized natives' lands and increased mineral production. Mineral exports doubled between 1965 and 1970 to 170 million pounds. In the district of Huambo, between 1968 and 1970 white-owned land more than doubled from 249,039 hectares to 526,270 hectares. Native-owned land decreased by 36.5%. The average African farm's gross income declined between 1964 and 1970 from $98.00 to $35.00[3]Portuguesepetroleum-production began in Congo Basin in the 1960s, and in the exclave of Cabinda in 1968. Now the petroleum industry is the engine of the Angolan economy.[4][5]