Year	% of total fuel combustion
1971	0
1972	1.7325017325017324
1973	1.6613418530351438
1974	1.7699115044247788
1975	1.7672151127361364
1976	1.820388349514563
1977	1.726121979286536
1978	1.668460710441335
1979	1.631578947368421
1980	1.8567639257294426
1981	1.8329938900203666
1982	1.720019111323459
1983	1.9283746556473826
1984	1.76444640494045
1985	1.563142739613328
1986	3.9296407185628746
1987	3.9323904794756808
1988	4.105571847507331
1989	3.912363067292645
1990	4.297470283450167
1991	4.051620648259304
1992	3.853727144866386
1993	3.5860655737704916
1994	3.5364396654719235
1995	3.677289948740807
1996	3.7407013815090333
1997	3.9805036555645814
1998	4.21821131616305
1999	3.7672583826429977
2000	4.285974831296736
2001	3.7419814682822525
2002	3.308016877637131
2003	4.279390063944908
2004	4.2994932156285754
2005	3.776152406871917
2006	4.129032258064516
2007	3.890445066915655
2008	3.4124398945245855
2009	4.276315789473683
2010	3.872570510010229
2011	4.088888888888889
2012	3.688635747219963
2013	1.0345846881466154
2014	1.1130004637501931