Year	% of total fuel combustion
1971	17.889908256880734
1972	17.083333333333336
1973	17.786561264822137
1974	16.78832116788321
1975	15.838509316770185
1976	15.29745042492918
1977	16.799999999999997
1978	16.953316953316953
1979	20.14742014742015
1980	23.51543942992874
1981	27.1523178807947
1982	28.131416837782343
1983	21.255060728744937
1984	25.054466230936818
1985	24.825986078886313
1986	27.951807228915666
1987	29.195402298850574
1988	26.995305164319248
1989	27.966101694915256
1990	29.32038834951456
1991	27.852998065764023
1992	30.683918669131238
1993	27.88632326820604
1994	29.50819672131148
1995	31.05950653120465
1996	26.89335394126739
1997	26.964560862865948
1998	28.818443804034583
1999	24.00611620795107
2000	26.05633802816902
2001	24.082232011747433
2002	24.895104895104893
2003	27.10997442455243
2004	24.765258215962447
2005	27.012127894156563
2006	25.734549138804457
2007	26.135310472659874
2008	25.63884156729131
2009	26.61290322580645
2010	27.226277372262775
2011	26.89979825151311
2012	25.224148236700533
2013	24.600827912477826
2014	24.644808743169396