Year	% of total
1970	56.66735281403994
1971	54.870755198052365
1972	55.43309439814852
1973	52.57967573289088
1974	52.18788086131278
1975	51.594237423742385
1976	51.784158718929
1977	53.00063235395307
1978	54.15997597308986
1979	55.66340719297872
1980	56.66248077648491
1981	58.94415946759827
1982	60.292992569096135
1983	60.25072621495963
1984	60.690130305134595
1985	64.02239878193427
1986	63.90361855257897
1987	63.79978561015351
1988	65.53263396123675
1989	66.99532350390287
1990	74.11717495987159
1991	74.76051645147855
1992	73.90739939420165
1993	71.82506307821698
1994	72.12978369384359
1995	71.07942973523421
1996	70.52845528455285
1997	71.84388689765034
1998	71.9661733615222
1999	71.80919639020198
2000	69.30860033726813
2001	68.80851063829788
2002	71.44097222222221
2003	69.15927334178285
2004	68.68686868686868
2005	68.76779178527856
2006	69.67977300364817
2007	70.19945248337895
2008	71.62217659137578