Year	% of total
1970	41.67558986415648
1971	41.30302794369977
1972	41.932160248349994
1973	41.151132846128114
1974	41.966446989134006
1975	38.049306634379306
1976	38.39740975844057
1977	39.45362477423873
1978	41.04279175996544
1979	42.53096081777483
1980	45.92329070148977
1981	48.358760402008194
1982	52.634919712169356
1983	56.30387374317626
1984	56.66189616167131
1985	57.79983828852691
1986	57.73846687410741
1987	57.81333947019505
1988	56.28060731299257
1989	58.036002000380385
1990	38.415841584158414
1991	38.38383838383838
1992	17.53846153846154
1993	8.16326530612245
1994	8.571428571428571
1995	9.417040358744394
1996	15.936254980079681
1997	20.27027027027027
1998	22.699386503067483
1999	21.052631578947366
2000	20.670391061452513
2001	20.949720670391063
2002	27.796610169491526
2003	27.044025157232703
2004	26.785714285714285
2005	26.300578034682083
2006	25.82417582417583
2007	26.509186351706038
2008	25.64102564102564