Year	% of total energy use
1971	0.8902514187382579
1972	0.9023001576653785
1973	1.122264756351271
1974	1.9564776323587743
1975	1.3168028345491678
1976	1.660664943302214
1977	1.293976425177625
1978	1.0368756352441535
1979	3.6824639194630295
1980	6.919889307821038
1981	7.756824306758542
1982	8.800582836594009
1983	9.175530466194754
1984	10.020752222687152
1985	12.675667074091724
1986	15.468527173217058
1987	14.878874409774795
1988	14.56939850425819
1989	15.488022486715696
1990	15.403260643993754
1991	16.496742695720613
1992	16.720762490655726
1993	18.26742651543345
1994	20.544100252994177
1995	18.709277235739243
1996	18.071615052338622
1997	17.705394828157807
1998	18.620886288996232
1999	21.12877741343138
2000	25.824773515652527
2001	26.014382741523374
2002	26.977299860792357
2003	26.47688076960055
2004	26.055417538456844
2005	26.423127318679914
2006	27.09304303649704
2007	24.630561819108834
2008	25.767347271967445
2009	24.41404978393227
2010	24.036623115563238
2011	25.55051807954232
2012	26.85062182819122
2013	27.164276872601324
2014	28.297930450563136
2015	27.46779240203208