The two graphs show the main sources of energy in the USA in the 1980s and the 1990s, write a report to describe the changes occurred.

The pie charts compared the proportions of power sources falling into 5 distinct groups in the USA from 1980 to 1990.

It is clear that oil remained the major source of energy through the 10-year period while the percentage of hydroelectric power stayed the lowest.

In 1980, the oil segment counted for 42% of total power consumption but lost 9% share during the following decade, dropping dramatically to 33% by 1990. Meanwhile, natural gas and hydroelectric power were stable through 1980 to 1990, with the former category only saw a dip by 1% and reached to 25% later in 1990.

In contrast, as can be seen in the same period, percentage of nuclear power jumped from a mere 5% to 10%, which doubled its proportion of overall energy consumption. Turning to another important trend, the coal segment grew by 5% during the decade. This was 6% lower than the proportion of oil and 2% higher than that of natural gas, making it the second largest group of energy source.