Year	% of energy use
1971	62.41807772582087
1972	66.4596946193169
1973	68.64767324765722
1974	67.37636984735722
1975	65.60523409285027
1976	71.27265214257667
1977	74.15197144155722
1978	74.82376639367756
1979	77.37422027199999
1980	77.526899685333
1981	75.99097978768997
1982	76.77038580410647
1983	75.75926938134508
1984	75.03253519495514
1985	72.52665072887685
1986	69.78751602988737
1987	67.47347363412483
1988	71.02436164953527
1989	72.24319162656029
1990	75.65171218728372
1991	77.77377748751391
1992	81.60545665820543
1993	83.86996456003016
1994	85.40998504882455
1995	85.39013117074704
1996	85.70119886891734
1997	86.1420242069439
1998	82.6810792266207
1999	82.27800581526094
2000	81.69380516852388
2001	81.71118634826175
2002	82.43751680758301
2003	81.26003580381611
2004	81.60574079095683
2005	79.56049613696182
2006	79.51943234901742
2007	80.82952763522118
2008	80.29728486340183
2009	80.66200950022734
2010	82.01995071166279
2011	81.95030160919285
2012	82.44682462707352
2013	83.4730685229819
2014	81.70429565173532
2015	81.44832917317333