Year	% of total
1970	0.797744706692476
1971	0.8238458839728007
1972	0.8711683769070699
1973	0.7987780030626567
1974	0.6408576577052748
1975	0.6845892584716402
1976	0.6641898202092569
1977	0.6228122394670681
1978	0.6207049814338754
1979	0.6524316540493305
1980	0.6409342575388676
1981	0.5908294547796299
1982	0.6602059073123403
1983	0.6784099086090042
1984	0.671506785389909
1985	0.6915674197552819
1986	0.7751705154359076
1987	0.8566513493553661
1988	1.0189843010315098
1989	1.103440159033774
1990	0.6309148264984227
1991	0.6172839506172839
1992	0.6042296072507553
1993	0.591715976331361
1994	0.5714285714285714
1995	0.4830917874396135
1996	0.41753653444676403
1997	0.3683241252302026
1998	0.3289473684210526
1999	0.2971768202080238
2000	0.27100271002710025
2001	0.26041666666666663
2002	0.2503128911138924
2003	0.24154589371980675
2004	0.2331002331002331
2005	0.22522522522522523
2006	0.2120890774125133
2007	0.2004008016032064
2008	0.19011406844106463