Year	% of total energy use
1971	0.22890761569961454
1972	0.2387677367204391
1973	0.20586290995237094
1974	0.37336481645338937
1975	0.35711777451374394
1976	0.27669463168670627
1977	0.35208745052861407
1978	0.3468775903411364
1979	0.4073896017211849
1980	0.4393447193336741
1981	0.3766992975318743
1982	0.3004923433768398
1983	0.4053548169517116
1984	0.8872217698734755
1985	1.56019829435858
1986	3.52367949346684
1987	5.825359253637438
1988	6.455807218254858
1989	6.878668576466571
1990	6.782362917626374
1991	7.216661467910352
1992	7.545964248393153
1993	8.06349334778496
1994	8.579074512325661
1995	8.081060845157467
1996	8.190492212868318
1997	7.911476972097511
1998	8.549988530816645
1999	9.358994610220272
2000	9.032521413366549
2001	9.571058511684475
2002	11.972188407732341
2003	15.50635097920949
2004	15.551916790923546
2005	14.869604081968625
2006	15.314302725479164
2007	15.321082523879278
2008	15.944253693549234
2009	17.52323837123884
2010	17.321530028249043
2011	18.440546591330538
2012	19.938498453097857
2013	20.77952410447643
2014	20.848848851394596
2015	18.95657255673658