Year	% of total fuel combustion
1971	53.54330708661418
1972	54.22535211267606
1973	51.533742331288344
1974	57.59493670886076
1975	56.896551724137936
1976	60
1977	51.75438596491229
1978	53.68852459016394
1979	55.144032921810705
1980	61.57407407407407
1981	58.415841584158414
1982	62.5
1983	63.00578034682081
1984	63.043478260869556
1985	61.53846153846154
1986	63.59223300970874
1987	62.72727272727272
1988	67.53246753246754
1989	63.87832699619772
1990	61.15384615384616
1991	59.78260869565217
1992	62.17616580310881
1993	64.82939632545933
1994	58.42696629213483
1995	58.33333333333333
1996	62.589928057553955
1997	65.52567237163814
1998	65.05494505494505
1999	67.32456140350878
2000	66
2001	64.5621181262729
2002	69.9203187250996
2003	67.48120300751879
2004	72.31638418079096
2005	69.11764705882352
2006	66.33165829145729
2007	63.868065967016484
2008	65.26946107784431
2009	69.49685534591194
2010	68.98638426626323
2011	68.63905325443787
2012	69.5906432748538
2013	67.60168302945301
2014	68.6192468619247