Year	% of total
1970	9.461158255024776
1971	9.71879065605795
1972	9.872752038009141
1973	9.011815088777041
1974	11.426979430736807
1975	10.50158298522071
1976	10.268312519995934
1977	8.740070902950189
1978	10.445907466117738
1979	9.425429447557166
1980	7.602189369472531
1981	8.822843639469857
1982	7.666143757458771
1983	8.467361486017298
1984	8.579980304125566
1985	9.560694748676031
1986	9.57064738221347
1987	9.161408232623355
1988	9.832956967331183
1989	8.882306552290087
1990	7.07070707070707
1991	7.07070707070707
1992	7.000000000000001
1993	6.9306930693069315
1994	6.862745098039216
1995	6.9306930693069315
1996	11.864406779661017
1997	13.793103448275861
1998	14.285714285714285
1999	14.814814814814813
2000	15.384615384615385
2001	11.267605633802818
2002	10.38961038961039
2003	7.82608695652174
2004	7.142857142857142
2005	7.5
2006	5.172413793103448
2007	5.389221556886228
2008	7.43801652892562