Year	% of total
1970	15.682103852655843
1971	15.98404556182071
1972	16.2278192627071
1973	15.517355793189362
1974	18.740369058966074
1975	18.74331208427173
1976	18.569398082735354
1977	17.015213221071555
1978	19.43129313495949
1979	18.58732281445661
1980	15.451998320397403
1981	17.21687861403764
1982	16.106892534466315
1983	17.109947604142214
1984	17.63786374649551
1985	19.195624630501438
1986	19.556879842975317
1987	18.98015882509539
1988	20.348663027531842
1989	19.53441797812886
1990	68.18181818181817
1991	30.382513661202186
1992	19.832402234636874
1993	14.21188630490956
1994	11.676159479251425
1995	12.047697368421053
1996	11.209439528023598
1997	11.556503198294244
1998	11.726525313717005
1999	11.780219780219781
2000	12.311111111111112
2001	14.21889616463985
2002	16.502463054187192
2003	17.497348886532343
2004	15.714285714285714
2005	21.17283950617284
2006	22.426721199727336
2007	24.94365138993238
2008	26.621160409556317