Africa- Oil Prices

Currently, crude oil is about $85/barrel against average historical $100/barrel. We are all enjoying this sharp drop in oil prices for obvious reasons. It has a two-edge benefit for all of us- we get to buy at "happy" prices at the pump, we have extra money to spend on other things of interest (which stimulates the economy) and just the great feeling at the pump that we are not breaking the bank.

  However, this has a negative effect in some parts of the world like Nigeria & Venezuela that depend on oil for its revenue- total national income for expenditures on social & economic budgets. This means as we enjoy cheaper prices at the pump in the U.S, these countries and some companies that depend on high prices to thrive are scared.

Here's my question- Why do these countries primarily depend on crude oil sales as its major income source? Why is agriculture, manufacturing and even other natural resources not fully utilized? Maybe because "we" think oil will be here forever, or that oil is in a high demand that we will always be safe. Actually, the U.S is making headway to be the top energy producer in the world, especially with technology investment on Shale Oil.

We know oil prices will not stay low for too long (just like anything) but perhaps, it will trigger strategic thoughts on diversifying the economy so we are not depending solely on one product.

Fun Fact: Nigeria exports ~1,000,000 barrels of oil/day, that's $85M/day against $100M/day avg historical daily income.

Thanks for reading.
Ony.