Year	% of total
1970	18.090450950464827
1971	18.165824964621237
1972	18.584542367076686
1973	18.347622189352258
1974	19.21668785110741
1975	19.711377573638064
1976	20.201692531407186
1977	20.32730483385541
1978	21.232658845667583
1979	21.10095498991744
1980	20.327056899641576
1981	20.85496723099239
1982	20.440526540539537
1983	20.601067841689495
1984	21.022867184738615
1985	21.32779101124815
1986	21.6745344670838
1987	21.37975068581987
1988	22.714029697068224
1989	22.808978876764442
1990	94.96124031007753
1991	83.05647840531562
1992	74.05247813411079
1993	67.3521850899743
1994	61.89376443418014
1995	65.70743405275779
1996	68.51851851851852
1997	74.12398921832884
1998	78.97727272727273
1999	84.11214953271028
2000	90.9090909090909
2001	91.7933130699088
2002	92.797783933518
2003	92.79538904899135
2004	91.25874125874127
2005	93.22033898305084
2006	93.35347432024169
2007	93.58600583090379
2008	93.35443037974683