Year	% of total fuel combustion
1971	26.443768996960486
1972	25.72614107883817
1973	24.009603841536613
1974	22.087912087912088
1975	22.36024844720497
1976	21.394910461828466
1977	21.735395189003434
1978	20.819935691318328
1979	21.605401350337583
1980	18.932748538011694
1981	18.47041847041847
1982	19.09028256374914
1983	17.462393721386526
1984	16.442738323736403
1985	16.04179471419791
1986	16.477611940298505
1987	16.841491841491845
1988	16.870824053452115
1989	17.877382792375066
1990	19.79643765903308
1991	21.019417475728154
1992	21.64482602801627
1993	22.85464098073555
1994	22.56902761104442
1995	22.93824319140775
1996	24.863813229571985
1997	25.42814594192107
1998	26.397966594045023
1999	26.68500687757909
2000	27.65741367637102
2001	26.654240447343895
2002	26.972697269726975
2003	28.34240774349667
2004	26.977128685588315
2005	26.202108511185397
2006	26.132404181184672
2007	27.24609375
2008	28.608187134502927
2009	30.290262172284642
2010	29.619151251360172
2011	28.670911261440512
2012	28.251207729468597
2013	29.93857737269665
2014	28.845791752965543