Year	% of total fuel combustion
1971	19.92063492063492
1972	18.98376852505293
1973	17.78816199376947
1974	17.418439716312058
1975	20.539254559873115
1976	20.520752771332816
1977	21.311475409836067
1978	24.885757806549886
1979	27.392183288409704
1980	29.19070868471667
1981	28.94088669950739
1982	27.87686616461884
1983	28.995494301616752
1984	24.79770294962151
1985	28.787698176183095
1986	30.23554603854389
1987	27.157916710155515
1988	28.86637354234372
1989	26.249313563975836
1990	22.876988572708942
1991	21.243953006219765
1992	21.288588844464833
1993	21.547927851842914
1994	23.30423102753526
1995	24.922850844966938
1996	23.64594015102079
1997	23.23317816335167
1998	21.429747304304883
1999	25.887957317073173
2000	22.838007206642647
2001	22.729260825193176
2002	21.11861137897782
2003	24.232214591162368
2004	25.473997404488337
2005	25.599648373728495
2006	30.861075167627334
2007	30.245308614062854
2008	27.494716399154623
2009	26.410389895059865
2010	24.591904445919045
2011	20.15338619524243
2012	18.08336738863915
2013	17.95115604043639
2014	18.395070212814698