(the main sources of energy in the USA in the 1980s and the 1990s) IELTS writing

The two graphs show the main sources of energy in the USA in the 1980s and the 1990s.

Write a report for a university lecturer describing the changes which occurred.
Write at least 150 words.

My answer:
The two given pie graphs provide information for relative percentage of the main energy resources in the USA during two consecutive decades. In general, as can be seen, there is not a great deal of differences in pattern of two decades.

In 1980s, the oil played an important role in providing energy sources, accounting for 42% of total energy resources. Natural gas and coal each respectively with 26% and 22% standed out noticeably in next positions. Non-fossil fuels such as hydroelectric and nuclear powers, combined totally made up just 10% of overall energy sources.

Over the next decade, consumption of oil decreased significantly by 9% whereas the pattern of consuming of other fossil fuels remained fairly similar. In contrast, the remarkable evident difference was visible growth of nuclear power as a new source of energy from 5% to 10%.

In conclusion, it seems fair to say that there was an evident trend to reduction in consumption of fossil fuels and in particular the oil over the recent decades.

"there is not a great deal of differences in pattern of two decades."
--> personally, I think this sentence is redundant, because if there is no great difference, why can you still write so much about the graphs.

As to other part, you did a really great job, I think you can get a really good grade in the IELTS test.