Year	% of total
1970	25.381067481957853
1971	24.578959245670102
1972	22.90192115400729
1973	21.28850618170373
1974	19.904917260389944
1975	39.20573940053798
1976	39.0724129124958
1977	36.83250206941035
1978	32.754435857504376
1979	29.608892232590968
1980	19.40840457805481
1981	20.038017355347254
1982	17.75340008373805
1983	18.737966772073474
1984	15.312396215853
1985	11.100607713590847
1986	12.731153403091099
1987	12.097867590527265
1988	12.683388079660396
1989	12.353768060634032
1990	3.7037037037037033
1991	3.571428571428571
1992	3.3333333333333335
1993	3.125
1994	2.941176470588235
1995	2.857142857142857
1996	2.7777777777777777
1997	2.7027027027027026
1998	2.5
1999	2.4390243902439024
2000	2.5
2001	2.3255813953488373
2002	2.3255813953488373
2003	2.3255813953488373
2004	2.1739130434782608
2005	1.9607843137254901
2006	3.8461538461538463
2007	3.7735849056603774
2008	3.508771929824561