Year	% of energy use
1971	61.28071161701509
1972	61.67478881982894
1973	64.95796805146271
1974	67.02157366616758
1975	67.58124331424904
1976	69.00901570265448
1977	70.34376449653166
1978	71.59717728452559
1979	73.07162763498827
1980	73.83362641866493
1981	74.46783436206414
1982	75.59468620852347
1983	76.10484217536427
1984	75.88169236122219
1985	76.18909389810378
1986	76.41069956613414
1987	77.95800338462283
1988	78.537384176655
1989	81.04320657516743
1990	80.98457525543506
1991	80.94481941739375
1992	82.07474170883474
1993	82.88544412923918
1994	83.24972320646543
1995	83.16482040291892
1996	83.40154258472509
1997	84.17317014052406
1998	85.13893473107854
1999	87.32164321417703
2000	87.73486438114872
2001	88.27102886548285
2002	88.38246715448844
2003	87.8022726297925
2004	81.89936125291864
2005	84.38220969802592
2006	85.5719901694836
2007	86.86636006858186
2008	88.3165600830087
2009	88.54313961132439
2010	88.7646796056595
2011	90.48261151301085
2012	90.9405998998956
2013	90.24558494479781
2014	90.72183409217001