The two main graphs illustrate the basic source of energy in the USA in the 1980s and the 1990. Overall, in 1980, the highest percent was oil and natural gas and the lowest was coal and hydroelectric power , while the largest persent was natural gas and oil the lowest percent was hydroelectric power in 1990.
In 1980, it is clear that the highest persent is oil 42 %. The next highest percent of natural gas is 26 % and coal was 22 %. The lowest persent is hydroelectric power and nuclear power 5% respectively.
Looking more closely at the pie chart, it can be seen that , in 1990, the percentage of oil was descreased from 44% to 33%. Natural gas and coal percent was almost same 25% and 27% respectively. The proportion of nuclear power was slightly increased from 5% to 10%. The lowest percentage was always similar 5%.