In 11 months, the price of a barrel of oil has gone from $145 to $30 and it is again pointing up. But whether prices are high or low, natural resources such as minerals or oil are a mixed blessing for ordinary people in countries that sell them.

Countries too dependent on extractive industries face three problems. Large foreign exchange inflows lead to the “Dutch disease”: local costs go up, so imports undercut domestic manufacturing and agriculture. Gyrating commodity prices play havoc with budgets. And mineral rents infest politics with corruption and conflict. As everyone fights over the mineral cake, good governance falls apart.