Year	% of total
1970	75.30639184859169
1971	75.24014778594595
1972	74.93766422928005
1973	74.13057711861832
1974	74.24973692454648
1975	73.9193138772974
1976	74.02338823989125
1977	72.76051901085778
1978	72.88949613149023
1979	72.84752574380204
1980	71.85364309330936
1981	69.91184212854701
1982	70.1298769805137
1983	68.56019135460464
1984	68.67506773377774
1985	67.22771528909804
1986	66.60543455108684
1987	65.3488935375429
1988	64.47580924411749
1989	63.37299353683681
1990	75.50387596899225
1991	76.02523659305994
1992	75.52
1993	75.77741407528642
1994	76.56765676567657
1995	76.16666666666667
1996	76.1744966442953
1997	76.04166666666666
1998	76.40845070422534
1999	76.3963963963964
2000	76.45985401459853
2001	76.49186256781194
2002	76.45985401459853
2003	76.67910447761194
2004	76.37051039697542
2005	76.9811320754717
2006	77.35849056603774
2007	77.90476190476191
2008	78.63894139886578