Year	% of total fuel combustion
1971	3.4891165172855314
1972	3.2700620184175904
1973	3.0867346938775504
1974	3.212475633528266
1975	3.508771929824562
1976	3.37558556076054
1977	3.306106573317775
1978	3.1736702909197763
1979	3.1615606464602477
1980	3.070153996577853
1981	2.9387643521049753
1982	2.896222318714721
1983	2.5383205970416047
1984	2.4118738404452684
1985	2.36021237763398
1986	2.2976523080772275
1987	2.3456295108259826
1988	2.453172205438066
1989	2.0459577066951677
1990	1.9971191653365516
1991	1.934193782948555
1992	1.9250143926309724
1993	1.8844133099824867
1994	1.6427370327253907
1995	1.795769811839033
1996	1.8544046212419594
1997	1.8642965532191629
1998	1.7378207727509705
1999	1.9714702641531905
2000	1.8352705633724482
2001	1.8114735907678652
2002	1.7092391304347823
2003	1.7425855710798317
2004	1.7842186746529276
2005	1.8116736065454015
2006	1.843176949695157
2007	1.882990550305726
2008	1.9479918563760876
2009	2.0379247644461236
2010	1.9568443886288398
2011	1.9463116734765609
2012	2.0583865046761645
2013	1.9905826694338447
2014	2.0699897892880346