Year	% of total fuel combustion
1990	1.635671073269101
1991	1.7469560614081523
1992	1.1939218523878437
1993	1.7952635599694424
1994	1.9649984648449494
1995	2.0150375939849625
1996	1.8305084745762714
1997	1.8487394957983194
1998	1.710526315789474
1999	1.7987633501967397
2000	1.773049645390071
2001	1.7946687780416997
2002	1.7371601208459213
2003	1.7412935323383085
2004	1.7385705086928525
2005	1.7675192347681428
2006	1.8089430894308942
2007	1.8631314940881403
2008	1.8603827072997876
2009	2.9635562675210254
2010	2.671353251318102
2011	3.107801877630301
2012	3.339575530586767
2013	3.389830508474577
2014	3.5074626865671643