Year	% of total fuel combustion
1971	23.703703703703702
1972	26.666666666666668
1973	25.000000000000007
1974	25.683060109289617
1975	24.18604651162791
1976	26.893939393939398
1977	28.21428571428572
1978	26.190476190476186
1979	25.43352601156069
1980	29.00232018561485
1981	34.79087452471483
1982	29.215358931552586
1983	30.93415007656968
1984	38.27683615819208
1985	38.01874163319947
1986	38.106796116504846
1987	42.3963133640553
1988	40.07134363852556
1989	40.070505287896594
1990	38.387096774193544
1991	41.90782422293676
1992	42.33983286908079
1993	43.027522935779814
1994	42.02772963604853
1995	42.74061990212072
1996	44.03162055335968
1997	43.202416918429
1998	44.90538573508005
1999	43.75000000000001
2000	41.02564102564103
2001	41.53846153846154
2002	44.26877470355732
2003	40.96064042695131
2004	40.142517814726844
2005	39.039204859193816
2006	41.51351351351351
2007	43.19710294878428
2008	48.09651474530831
2009	46.60144181256437
2010	48.41101694915255
2011	50.57701956848971
2012	49.91220368744513
2013	52.003561887800544
2014	52.42637909581087