Year	% of total
1970	61.20304293557536
1971	62.75166367069082
1972	63.589262788808675
1973	64.01782289743682
1974	66.09633164587065
1975	69.78431310175442
1976	70.86669420241266
1977	71.13386401671733
1978	72.29123372929345
1979	71.7458879982409
1980	72.49758287693393
1981	71.31893514857401
1982	71.83709216054253
1983	70.93284399577624
1984	70.10329465617824
1985	69.15615464165714
1986	68.62753186796623
1987	68.36518370796585
1988	67.18742010198395
1989	65.53936627659172
1990	56.92883895131086
1991	56.10687022900763
1992	51.45228215767634
1993	51.028806584362144
1994	51.91489361702127
1995	51.04602510460251
1996	51.04602510460251
1997	48.728813559322035
1998	46.3519313304721
1999	43.946188340807176
2000	43.859649122807014
2001	42.410714285714285
2002	42.53393665158371
2003	39.91416309012876
2004	40.50632911392405
2005	39.224137931034484
2006	39.57446808510638
2007	39.57446808510638
2008	38.333333333333336