Year	% of total
1970	68.11565967223395
1971	68.42891231165392
1972	67.43395964460105
1973	67.43976338991317
1974	68.51326692362223
1975	67.60329231751481
1976	67.28169972346494
1977	64.20684232591076
1978	64.25896733492424
1979	63.84441705778679
1980	65.75085594860239
1981	65.8975529190326
1982	65.7754103969422
1983	63.97874255585351
1984	64.06521552026211
1985	64.53265300177341
1986	64.27245166553698
1987	66.61099593321089
1988	67.09734115718354
1989	65.15757817066049
1990	66.92913385826772
1991	67.1875
1992	69.06474820143885
1993	67.88321167883211
1994	65.92592592592592
1995	64.39393939393939
1996	63.07692307692307
1997	61.240310077519375
1998	58.4
1999	66.0377358490566
2000	64.51612903225806
2001	64.28571428571429
2002	61.111111111111114
2003	61.904761904761905
2004	60.83916083916085
2005	62.745098039215684
2006	57.961783439490446
2007	55.62130177514793
2008	51.13636363636363