As if a recession wasn’t enough bad news for South Africa, it’s now confirmed as the continent’s second-largest economy. The answer to the question of whether South Africa or Nigeria, the two countries that account for almost half of sub-Saharan Africa’s gross domestic product, is the biggest economy on the continent has long depended on which exchange rate you use for the West African nation. But now both the official naira rate of 306 per dollar and the weaker market exchange rate of around 360 that almost all investors use put Nigeria tops.