Luanda (AFP) - With oil prices collapsing over 50 percent in the past six months, Angola -- Africa's second-largest oil producer -- has had to introduce austerity measures and overhaul its budget to deal with a severe drop in expected revenue."We will go through a difficult time now because the government cannot afford to implement the budget they had adopted for the year," said Jose de Oliviera, an independent consultant in the oil sector.Angola draws about 70 percent of its income from its oil resources.