Year	% of total
1970	21.548281587116143
1971	29.84074864788358
1972	28.12552515838628
1973	25.606509104389175
1974	26.885532649582288
1975	26.939448665952415
1976	28.160847133609856
1977	24.138332654279328
1978	23.36471203967334
1979	20.373253632373842
1980	23.10746240529256
1981	25.359645926897116
1982	23.87487458207555
1983	23.995619591514373
1984	26.615153232356086
1985	26.05950000193204
1986	27.4547790100986
1987	24.743564672688965
1988	31.162975939463532
1989	30.669685324171947
1990	84.60648148148148
1991	82.86082474226805
1992	80.78602620087337
1993	77.83333333333333
1994	75.3479125248509
1995	76.13636363636364
1996	75.92592592592592
1997	76.92307692307693
1998	75.70422535211267
1999	76.52173913043478
2000	75.88532883642496
2001	77.22132471728594
2002	77.60736196319019
2003	77.61627906976744
2004	78.93258426966293
2005	78.87700534759358
2006	78.03547066848567
2007	76.0989010989011
2008	73.62637362637363