Year	% of total fuel combustion
1971	8.059626073774634
1972	7.854341194131033
1973	7.2206303724928365
1974	7.067771985300403
1975	6.959212823361371
1976	6.837890697073693
1977	6.275340614384338
1978	7.417218543046359
1979	6.82123526927949
1980	6.00759081872402
1981	5.376049340414596
1982	5.248466469088152
1983	5.306309159365212
1984	6.148349778836338
1985	6.164269819655252
1986	5.96579476861167
1987	5.824020147961593
1988	6.14333406133974
1989	6.554099772405733
1990	6.408856536245072
1991	6.408779482204571
1992	6.5465663499295585
1993	7.193431308383412
1994	6.759366550791813
1995	6.2579893759054634
1996	5.957886718537462
1997	5.863753213367611
1998	5.232205956587581
1999	5.563318325311807
2000	5.269394649925624
2001	5.865687541080211
2002	6.267956225190254
2003	6.1573118077717295
2004	5.911947223146644
2005	6.470004475491818
2006	6.945195949601917
2007	7.688445014785472
2008	7.934752557367987
2009	8.11586356253384
2010	4.766329410145226
2011	5.220966437873079
2012	6.145196128542927
2013	6.188048262976217
2014	6.071434048491724