Most important was the dramatic decline in oil prices in 2015, which resulted in a significant reduction in nominal GDP by 2050 - 51, of nearly $ 430 billion. (3dpolicy.ca)
Low oil prices in the early 1970's (around $ 3 a barrel) caused demand to soar. (sovereignman.com)
The price rise is due to the rise of oil prices on world markets. (globes.co.il)