The primary energetic resources for USA between 1980 and 1990 illustrated by the given pie charts.
Overall, it is clearly seen that the proportions of oil and natural gas decreased, while the other sources increased or remained stable over the given period of time.
In 1980, percentages of oil and natural gas consisted 42% and 26%, respectively. However, after a decade percentage of oil experienced noticeable decline to 33%, whereas natural gas saw negligible downward to 25%. Regardless of these facts, oil demonstrated the biggest proportion throughout the whole time frame, meanwhile the proportion of natural gas has been dropping to the third place.
Coal, which slightly increased its percentage for 5%, started from 22%, and reached 27%, by 1990. Hydroelectric power and nuclear power depicted the same results in 1980. Decade after, nuclear power has doubled its percentage, and approached 10%. Interestingly, hydroelectric power remained stable and did not change at all from initial 5%.