Nigeria's central bank has set about imposing strict capital and foreign currency controls in an effort to support the currency against the effects of a falling oil price. The efforts appear to be working to some extent, but some analysts predict the situation cannot last for long. "For the moment, the central bank may hold up the dam wall, but sooner or later the currency will weaken," said Goolam Ballim, group chief economist of Standard Bank in South Africa.

Central bank policy, said one