Nigeria: Oil Producer Imports Most of Domestic Oil Consumption

From The Guardian:

Many Nigerians believe that already widespread corruption became rampant under Jonathan, further undermining an economic system that sees Africa’s top oil producer import most of the 40 million litres consumed every day at heavily subsidised prices.

How are you the "top oil producer" and importing "most" of the 40 million litres used daily?

Probably Obama's fault.