Year	% of total fuel combustion
1971	10.078755856843786
1972	9.696051510273648
1973	9.018880647336479
1974	9.0625
1975	9.74402598406929
1976	9.15096991847062
1977	8.990114881111408
1978	8.75632197916032
1979	8.051310043668122
1980	8.079003523398342
1981	8.246523571878482
1982	7.329648381253194
1983	7.551345609065156
1984	7.504894496410704
1985	8.207252134223648
1986	8.396946564885496
1987	8.83583755131322
1988	8.37093690248566
1989	9.013951460543526
1990	9.966099747184556
1991	8.543191379012274
1992	8.123147474973434
1993	8.100198679052783
1994	8.645358488577376
1995	8.44404701073071
1996	9.144170869178284
1997	8.79153800064525
1998	7.804245988238812
1999	9.354350768250935
2000	8.920580280304895
2001	8.897214305415098
2002	8.928859679465006
2003	8.143559846966662
2004	8.795090290962076
2005	9.533902707644994
2006	8.640927132638549
2007	9.70992100624551
2008	8.741353850936504
2009	8.332700774252315
2010	7.3185416039523306
2011	7.439462296289476
2012	6.96439885610562
2013	6.82089399570391
2014	6.552071105148417