What did shell geologist M. King Hubbert predict?

Shell geologist M. King Hubbert predicted that the rate of petroleum production in the United States would peak around mid-century and then decline in a process called "Hubbert peak theory". This theory has been applied to areas other than the US and states that resource production will follow a bell-shaped curve with a rapid increase followed by a period of slower growth and then a rapid decrease as production is exhausted.