Year	% of total fuel combustion
1971	20.721845318860243
1972	20.674862673293223
1973	19.661178716296828
1974	17.96393305827268
1975	17.836434443963654
1976	15.719620099034014
1977	15.285819130718421
1978	17.484333034914954
1979	15.291219426359314
1980	15.033226062607094
1981	14.740908909865773
1982	14.914136892650768
1983	15.41039929609922
1984	15.151515151515152
1985	14.700148171254778
1986	14.835423197492164
1987	14.210603183876147
1988	15.157465997527092
1989	14.975810786597384
1990	15.201908449730327
1991	15.262030959317633
1992	15.813392032947524
1993	15.116400459338136
1994	15.610805641883813
1995	16.41546526867628
1996	15.84092423905799
1997	15.626230501287294
1998	15.140678567206523
1999	16.18395484408254
2000	15.808278075513975
2001	14.872644327377394
2002	14.965753424657533
2003	15.052770777714015
2004	14.853803881559115
2005	15.512638982382022
2006	16.093318419430684
2007	16.602333442372696
2008	16.114839520690985
2009	16.754622984041205
2010	17.414666282373286
2011	18.907939417928795
2012	18.830360012857604
2013	19.745479672924105
2014	18.950108940507402