Hard to be transparent about oil when...

... you don't know how much is being produced:

The Nigeria Extractive Industry Transparency Initiative (NEITI) has described the records of the country’s crude production and export as unclear, saying that after 58 years of oil production, the country does not know exactly the quantity it produces.

Speaking at the presentation of a research report on the Nigeria Extractive Industry in Abuja weekend, Chairman of the Board of NEITI, Prof. Asisi Asobie, said despite all the inroads made by the country to expand operations in the oil industry, it had not been able to get operators to tell the truth about the actual oil volumes produced.

“After 58 years of producing oil, Nigeria does not know how much was being produced. It is regrettable that we have not been able to get oil companies to tell Nigerians exactly what they produce. The sector is shrouded in secrecy,” he said.

I find it quite surprising the that the government wouldn't be able to strong-arm this information from oil companies who depend entirely on the continued legitimacy of their concessions. Have they tried?