The line graph compares the amount of fuel produced in a European country over a period of 29 years. It is clear that petroleum was by far the most important power source over the period shown. Natural gas provided the lowest amount of fuel from 1981 to 1997, but it overcame coal to take second place. In 1981, petroleum was the main source of fuel in Europe, generating around 100 million tonnes of oil. Coal produced approximately 80 million tonnes of oil, and natural gas provided minimum fuel this year. For the whole 14-year period, fuel produced by natural gas remained relatively stable. Between 1995 and 2000, fuel production from coal fell to only 45 million tonnes. By contrast, the figure for natural gas had doubled since 1995, to around 85 million tonnes. During the same period, petroleum fuel generation rose dramatically to a peak of 130 million tonnes by 1997, but it plummeted to around 120 million tonnes since 2000.