Year	% of total
1971	78.38861977506872
1972	74.44488108861125
1973	75.07038120066957
1974	71.96371011621704
1975	72.08831784531208
1976	71.22913035163535
1977	69.74072786610375
1978	71.05690680903402
1979	71.72689370963164
1980	74.1560315239799
1981	75.41183433056555
1982	76.1359591409234
1983	76.59978694275733
1984	75.85331254037955
1985	75.15568441784475
1986	73.53343032782084
1987	76.60911942832655
1988	73.28192341262385
1989	73.31880482660632
1990	74.93857896472682
1991	74.34111592873828
1992	75.48291205828728
1993	77.13286924849868
1994	76.41770968191325
1995	75.82322180687781
1996	76.39893851461159
1997	76.47347976739093
1998	73.94500344472371
1999	73.86948891105071
2000	73.52170477375026
2001	72.93905389181712
2002	72.25873316094383
2003	73.23732541811378
2004	73.18742277426992
2005	73.16971932807857
2006	72.73323695761586
2007	72.81048001585512
2008	72.24509004545901
2009	70.88495014670973
2010	69.9177864200529
2011	69.501043286841
2012	69.78043877906825
2013	68.47577241071258
2014	66.60676641226738
2015	65.92812674507582