Year	% of total fuel combustion
1971	17.5
1972	15.384615384615383
1973	7.352941176470589
1974	5.2631578947368425
1975	4.25531914893617
1976	3.783783783783784
1977	1.507537688442211
1978	2.13903743315508
1979	3.061224489795918
1980	4.545454545454545
1981	3.474903474903475
1982	4.059040590405904
1983	4.4673539518900345
1984	3.4129692832764507
1985	3.7288135593220333
1986	3.061224489795918
1987	3.3444816053511706
1988	3.5143769968051117
1989	3.858520900321544
1990	3.6809815950920246
1991	3.8461538461538463
1992	4.748603351955308
1993	4.404145077720208
1994	4.5893719806763285
1995	4.444444444444445
1996	4.8832271762208075
1997	5.304518664047151
1998	4.640371229698377
1999	4.057279236276849
2000	3.1674208144796387
2001	2.7842227378190256
2002	2.7522935779816513
2003	2.4761904761904763
2004	2.4390243902439024
2005	2.4896265560165975
2006	26.352288488210817
2007	27.046783625730995
2008	26.73130193905817
2009	13.055181695827725
2010	6.268221574344023
2011	6.704707560627675
2012	7.747489239598279
2013	6.131386861313868
2014	5.074626865671642