Year	% of total energy use
1971	0.8173855778546365
1972	1.0945682391623415
1973	1.1384935024314222
1974	1.447704233715215
1975	1.5351433799701133
1976	1.6255987156081007
1977	1.794234244916094
1978	1.720648869693666
1979	1.7534755196890863
1980	1.7708670970978704
1981	1.8201634520627585
1982	1.8499048103432312
1983	1.8112769861915188
1984	1.8077500668271818
1985	1.8370243654561418
1986	1.7980853021695484
1987	1.6468307431458635
1988	1.6310473823375344
1989	1.669004146418025
1990	1.1000014314184947
1991	1.1065834744346383
1992	1.1305476000207968
1993	1.1492849503836369
1994	1.0725701488126262
1995	1.0120045346207318
1996	1.0336450820570395
1997	0.9879974489284029
1998	0.9795431271376318
1999	0.985925986794079
2000	1.2091243714329467
2001	1.362449911387603
2002	1.3940180923907712
2003	1.507776014512381
2004	1.5741216271822795
2005	1.6063896539909448
2006	1.6751599356589733
2007	1.6753054287956557
2008	1.699308685269649
2009	1.7143612735553733
2010	1.8801747030153029
2011	2.0116881109168747
2012	2.1444784859437047
2013	2.2969466647237655
2014	2.166366322426384