Year	% of total
1970	67.25488659560827
1971	68.4726275529645
1972	66.68103901422532
1973	67.01086032473688
1974	70.44447270971543
1975	65.21988851249735
1976	67.91586238686268
1977	68.63957610740385
1978	69.35110909839779
1979	68.98468600441305
1980	70.40316910563241
1981	66.54836645796217
1982	62.874545171741524
1983	65.13218639770625
1984	66.44837591374633
1985	71.1952651567368
1986	71.15379908705928
1987	71.40745084989688
1988	71.17289764034267
1989	71.62320428838662
1990	73.33333333333333
1991	71.62162162162163
1992	70.81545064377683
1993	71.13821138211382
1994	70.54263565891473
1995	70.8
1996	70.41666666666667
1997	70.95435684647303
1998	71.30801687763713
1999	73.4126984126984
2000	73.06122448979592
2001	72.95081967213115
2002	75.18796992481202
2003	72.46963562753037
2004	73.22834645669292
2005	74.63235294117648
2006	73.88059701492537
2007	72.58687258687259
2008	75.59322033898304