LAGOS (Reuters) - Nigeria's GDP figures will shoot up by around 40 percent in the second quarter this year, when Africa's second-biggest economy changes the base year for its calculation to 2009 from the current 1990, a source close to the matter told Reuters on Wednesday.

The recalculation will enable Nigeria to join the ranks of middle-income countries and put it much closer in size to South Africa, the continent's most developed economy.

(Reporting by Chijioke Ohuocha; Editing by Tim Cocks)