Year	% of total fuel combustion
1971	5.940233236151603
1972	5.878308697146786
1973	5.81357583631049
1974	6.567258883248731
1975	6.272697259821722
1976	6.247997436719001
1977	7.43351489907081
1978	7.465437788018432
1979	9.088217880402604
1980	8.830677828787469
1981	8.625486922648859
1982	6.642478370080938
1983	9.594998640935037
1984	8.147138964577657
1985	7.898057027504417
1986	7.296969696969697
1987	8.576329331046312
1988	7.989926739926739
1989	8.8808337109198
1990	5.9869848156182215
1991	5.787852112676057
1992	5.659565310953304
1993	5.928338762214983
1994	5.3564236810310115
1995	6.914344685242517
1996	6.790835668369869
1997	6.6464339908952965
1998	7.518573551263001
1999	8.62092671524818
2000	6.671868903628561
2001	6.669052732044858
2002	6.888737820077046
2003	6.708380346702226
2004	7.16628086419753
2005	7.1782178217821775
2006	7.100085543199317
2007	6.9854702219383675
2008	6.779277580876253
2009	4.132000279661608
2010	4.001046025104601
2011	4.096598811480592
2012	4.58074074074074
2013	4.85201358563804
2014	4.839679358717435