Year	% of total fuel combustion
1971	8.059626073774634
1972	7.854341194131033
1973	7.220630372492836
1974	7.067771985300403
1975	6.959212823361372
1976	6.837890697073694
1977	6.275340614384338
1978	7.417218543046361
1979	6.821235269279488
1980	6.00759081872402
1981	5.376049340414597
1982	5.248466469088153
1983	5.306309159365213
1984	6.148349778836338
1985	6.164269819655252
1986	5.96579476861167
1987	5.824020147961592
1988	6.143334061339739
1989	6.554099772405734
1990	6.4088565362450725
1991	6.408779482204572
1992	6.5465663499295585
1993	7.193431308383412
1994	6.759366550791813
1995	6.2579893759054634
1996	5.957886718537463
1997	5.86375321336761
1998	5.232205956587581
1999	5.563318325311806
2000	5.269394649925624
2001	5.865687541080212
2002	6.267956225190253
2003	6.1573118077717295
2004	5.911947223146643
2005	6.470004475491818
2006	6.945195949601916
2007	7.68844501478547
2008	7.934752557367986
2009	8.11586356253384
2010	4.766329410145227
2011	5.220966437873082
2012	6.145196128542926
2013	6.188048262976217
2014	6.071434048491727