Year	% of total fuel combustion
1971	27.260505163191166
1972	26.26043673731535
1973	26.209052141887966
1974	27.153025720328387
1975	27.272727272727273
1976	28.022612857968145
1977	27.55543324422079
1978	28.19664295037964
1979	27.57581038689438
1980	26.688887766611114
1981	25.347658014960594
1982	24.7850269850963
1983	25.63059808089805
1984	24.93674444756818
1985	24.87622956159208
1986	22.624103545371103
1987	23.915476563549266
1988	22.688533247275238
1989	22.839003045772383
1990	22.166620601370326
1991	21.340343498072205
1992	20.79914082722917
1993	20.363626590698367
1994	20.70383680907066
1995	20.545596839712296
1996	21.312727700082263
1997	21.47379139366035
1998	20.98165098737181
1999	21.001137898397374
2000	21.184952023150732
2001	20.494023255340377
2002	20.662123677786816
2003	20.050718343467015
2004	20.273920486969754
2005	20.042074826464507
2006	20.592947275574677
2007	20.613505460042223
2008	20.084588056166467
2009	18.3721797663142
2010	19.272860218548157
2011	19.928543072647876
2012	18.17148363685641
2013	18.093061441853237
2014	17.36499707574893