During which years did the net U.S. import of petroleum drastically decrease?

The net U.S. import of petroleum experienced a significant decrease during the years from 1977 to 1982 due to several key factors.

During this period, the United States faced an energy crisis, which led to increased focus on energy efficiency and alternative energy sources. The 1970s energy crises, particularly the oil embargoes, highlighted the country's dependency on foreign oil, prompting policy changes and the development of domestic energy resources.

Additionally, in the late 1970s and early 1980s, efforts were made to reduce energy consumption and increase domestic production of oil, which had a considerable effect on imports. These efforts included improvements in fuel efficiency in vehicles, the promotion of energy conservation measures, and the emergence of policies aimed at exploring alternative energy sources.

As a result, the combination of energy awareness, conservation efforts, and rising domestic oil production contributed to a notable decrease in net petroleum imports during this time frame. This trend was particularly observable from 1977 to 1982, making this answer a clear reflection of the historical context of U.S. petroleum imports during those years.