Year	% of total
1970	5.836037860105369
1971	6.019930143974917
1972	6.363895900925852
1973	7.110864499750669
1974	7.402586604816963
1975	8.091152718068223
1976	9.035625034448547
1977	9.413125640564244
1978	9.484038278470866
1979	8.461137008729544
1980	7.954648368692324
1981	7.588510034824049
1982	8.749858323755637
1983	9.284454320671012
1984	9.58617938964452
1985	10.400800358311262
1986	9.369417390666813
1987	9.449161256142988
1988	9.962228863074085
1989	9.025347145344885
1990	12.761151891586675
1991	12.750949538795442
1992	11.9960668633235
1993	13.40042372881356
1994	13.429010763710917
1995	12.066574202496533
1996	10.845896147403684
1997	9.636295463067118
1998	8.764121876069838
1999	8.341543513957307
2000	7.809110629067245
2001	8.11222933821287
2002	8.242566970856638
2003	8.419243986254296
2004	8.477842003853564
2005	8.679245283018867
2006	8.324847250509166
2007	8.645833333333334
2008	8.863096808230019