Year	% of total fuel combustion
1971	8.059626073774634
1972	7.854341194131034
1973	7.220630372492836
1974	7.0677719853004035
1975	6.959212823361371
1976	6.837890697073693
1977	6.275340614384338
1978	7.417218543046361
1979	6.82123526927949
1980	6.00759081872402
1981	5.376049340414597
1982	5.248466469088152
1983	5.306309159365212
1984	6.148349778836337
1985	6.164269819655252
1986	5.96579476861167
1987	5.824020147961592
1988	6.143334061339739
1989	6.554099772405733
1990	6.4088565362450725
1991	6.408779482204572
1992	6.5465663499295585
1993	7.193431308383413
1994	6.759366550791813
1995	6.257989375905462
1996	5.957886718537463
1997	5.863753213367608
1998	5.232205956587581
1999	5.563318325311805
2000	5.269394649925624
2001	5.865687541080211
2002	6.267956225190255
2003	6.157311807771729
2004	5.911947223146645
2005	6.470004475491817
2006	6.945195949601916
2007	7.688445014785472
2008	7.934752557367984
2009	8.11586356253384
2010	4.766329410145226
2011	5.220966437873079
2012	6.145196128542929
2013	6.188048262976217
2014	6.071434048491726