This pie chart illustrates the five major energy sources in USA, during the years 1980 and 1990.
Overall, the major source of energy was oil, followed by natural gas, in the year 1980. Comparatively, in the year 1990, coal emerged as the second major energy source for USA, while oil remained the major source.
In terms of percentages, the highest contribution to energy was from oil, in both 1980 and 1990. In the year 1990 however, the percentage contributed by oil decreased by 9%. The second largest source of energy in the year 1980 was natural gas (exactly 26%), as compared to coal in 1990 (exactly 27%). The energy derived from natural gas and coal switched roles for the second and third major energy sources, from natural gas being second in 1980, to being third in 1990.
Other sources which contribute to the energy include hydroelectric and nuclear power. In 1980, both the sources were contributing to only 10% (5% each) of the total energy generation. However, the contribution of nuclear power significantly rose to 10% over the period of 10 years.