Year	% of total fuel combustion
1971	21.736862693962706
1972	22.087763613934094
1973	22.30926967769073
1974	22.74271496243839
1975	23.154118802579323
1976	24.094601776630476
1977	24.80284573307829
1978	26.08355876164713
1979	24.4861665099972
1980	23.857643970543823
1981	24.847145646064405
1982	25.06357618465242
1983	26.400814764087166
1984	27.402196000751346
1985	27.60988119197559
1986	26.203115892944343
1987	26.15829973267166
1988	25.734686734336716
1989	25.379875174466072
1990	26.053847169064277
1991	26.144959604795964
1992	25.76767926236931
1993	25.7413186595062
1994	25.366053588810907
1995	24.373407921682233
1996	24.587558868567797
1997	23.881389769043388
1998	24.40373661426293
1999	24.569593373229676
2000	24.954091174504317
2001	24.289426280467396
2002	24.57708779443255
2003	24.558646962038456
2004	24.420871679839
2005	24.322807933194156
2006	24.33971362860746
2007	24.25869497309435
2008	24.36018693668633
2009	24.77585701728684
2010	24.264344010171023
2011	24.01972047672804
2012	24.433799979091233
2013	24.336782734567873
2014	24.62089433754612