Year	% of total fuel combustion
1960	20.095408467501493
1961	19.19561243144424
1962	18.29465731246627
1963	20.25628388368655
1964	17.26618705035971
1965	16.596104995766296
1966	16.440366972477065
1967	17.849898580121703
1968	17.24678582627783
1969	17.50285062713797
1970	18.360914105594958
1971	26.772158019438134
1972	26.70094667302322
1973	26.49219515794133
1974	26.5710578703933
1975	26.953258905822953
1976	27.364710546501307
1977	26.863651558512505
1978	27.598312370641622
1979	27.87039764359352
1980	27.710652376193266
1981	27.376936450683758
1982	27.237850873676226
1983	26.040817298249582
1984	24.231300345224398
1985	24.110522331566994
1986	23.728521967269522
1987	23.65076487708592
1988	23.1489582162355
1989	22.83751688166535
1990	21.246659623391956
1991	20.570770818448835
1992	20.034867395899226
1993	18.987144004999553
1994	18.972915038043457
1995	19.34671498303068
1996	19.161939426793932
1997	19.285532321083828
1998	19.25204881577855
1999	19.025195606919823
2000	18.73194212607377
2001	17.908879766663066
2002	18.386647321031045
2003	18.34924811177391
2004	18.347222453906152
2005	18.913487318385485
2006	19.668829375134578
2007	19.464848278772138
2008	19.177866731678158
2009	19.404431238292098
2010	20.50755373136238
2011	20.24613676320903
2012	19.228118538938666
2013	19.844933861432764
2014	19.608114889244668