Hubbert peak theory predicts that oil-field production eventually reaches a peak and then declines.
The theory was proposed by American geoscientist M. King Hubbert in 1956. He modeled production as a roughly bell-shaped curve: output rises as discoveries and infrastructure expand, reaches a maximum when a significant share of recoverable resources has been produced, and then falls as remaining extraction becomes more difficult.
Hubbert famously predicted that United States crude-oil production would peak around 1970. U.S. lower-48 production did reach a peak near that time, although later technological changes and unconventional production altered the broader national pattern.
The theory concerns production rates, not the date when oil physically runs out. Estimates depend on definitions of reserves, prices, technology, discoveries, and extraction methods. For that reason, analysts apply the concept to particular fields, regions, or countries rather than treating one universal peak date as certain.