Year	% of total
1960	67.35579879267564
1961	69.29536272362768
1962	68.979503363447
1963	70.83497012005533
1964	71.45440443512217
1965	71.59104858258469
1966	70.4940189590892
1967	72.46605771092295
1968	73.1683342988945
1969	74.70312417556369
1970	78.36644683549312
1971	80.11409854643303
1972	80.42129493521655
1973	81.61574752364415
1974	81.90369111674644
1975	84.24607513869017
1976	85.37395232636999
1977	81.54773595758773
1978	81.25863103324987
1979	82.18049576424315
1980	84.32209903382827
1981	85.40409817597747
1982	85.28487465407048
1983	85.33380440652861
1984	84.55017051946894
1985	81.40423360480243
1986	84.21853762950956
1987	83.11159139066501
1988	82.13302383104161
1989	84.22662149777894
1990	80.44667749690223
1991	80.59660962361585
1992	83.56345603491293
1993	81.96160608149476
1994	80.82210984357947
1995	83.17811229319737
1996	80.55177441151767
1997	81.02220836467544
1998	83.49736503704405
1999	86.50723681452426
2000	84.03616853374484
2001	83.38537540083826
2002	85.2567327492204
2003	81.77346365857173
2004	82.75609099717434
2005	84.12212742186279
2006	80.8164495069197
2007	79.24051752370187
2008	78.63659452554116
2009	78.08765699434852
2010	75.12558464679661
2011	75.65654081341847
2012	75.81242013719098
2013	73.3496291275565
2014	72.81272629975807
2015	77.02412255583903