Year	% of total
1970	80.86423065913104
1971	80.71906929016036
1972	79.66121268107193
1973	78.90840416071507
1974	78.1833514336079
1975	78.04030823444901
1976	78.00581837696743
1977	78.21315956279712
1978	76.60686931766782
1979	75.79613200362499
1980	76.9011213612166
1981	76.42747470044135
1982	76.81779989934685
1983	73.38665656404609
1984	71.42542371962952
1985	70.6787464771911
1986	70.74171073352962
1987	70.61168044159452
1988	70.0118647022361
1989	69.17324779663669
1990	12.5
1991	12.31527093596059
1992	11.750599520383693
1993	10.955710955710956
1994	13.350785340314136
1995	15.522388059701491
1996	18.81533101045296
1997	21.367521367521366
1998	27.956989247311824
1999	37.5
2000	59.55056179775281
2001	56.470588235294116
2002	54.761904761904766
2003	56.52173913043478
2004	57.57575757575758
2005	58.82352941176471
2006	57.407407407407405
2007	54.95495495495496
2008	57.599999999999994