Nigeria, March 30 -- Over a week ago, Nigeria's finance minister, Zainab Ahmed, stirred controversies when she said that Nigeria had adopted a new flexible exchange rate policy for official transactions.

"The government will start to use the flexible rate, that has until now applied to investors and exporters, for government transactions too," a report by Bloomberg quoted Mrs Ahmed as telling journalists at the State House in Abuja.

"Within the government and the central bank, there is only one official rate and that's the Nafex rate."

The minister, by implication, suggested that the government had effectively devalued the naira yet again, just barely a year after the local unit was devalued twice. But the Central Bank of Nigeria swift...