Year	% of total
1971	42.59980624179125
1972	45.392973198576165
1973	42.61337680712458
1974	46.03415590467969
1975	44.318716039239916
1976	47.07522412606253
1977	45.93852393103374
1978	41.76468866294974
1979	42.52808782603276
1980	43.61478346829906
1981	45.76294744117801
1982	48.36814177261085
1983	48.565580252006725
1984	49.39059180241502
1985	53.09647958874021
1986	54.16950585979438
1987	58.332635370741926
1988	56.764762604499744
1989	57.77341355833615
1990	55.47364098530486
1991	56.86808329129241
1992	56.90546687189032
1993	58.82770829892058
1994	57.0301190681757
1995	59.07532423166256
1996	59.60480415746833
1997	58.420420449585464
1998	56.6585616901328
1999	57.175042177550026
2000	58.390725356633745
2001	58.926272082518594
2002	59.207548114683405
2003	57.447687395722646
2004	56.98276290442747
2005	55.93888605151265
2006	55.96825504376229
2007	55.5519834573161
2008	58.38076492502062
2009	57.34444027391821
2010	57.808228911435954
2011	57.96445982927868
2012	62.27299849545334
2013	62.928947508598654
2014	65.09801529355964
2015	66.06717867631144