Year	% of total
1970	32.13611996336074
1971	26.31737462753155
1972	21.86276922215064
1973	19.54459001421263
1974	15.25105871402327
1975	13.750228536276795
1976	14.537926305842298
1977	15.49966245751286
1978	16.316318856647406
1979	14.600899225274478
1980	12.240460085846923
1981	11.393535713291968
1982	9.443699336320247
1983	8.330014162464987
1984	6.735469422617014
1985	6.926285127265751
1986	8.841330843342812
1987	7.618005841831903
1988	9.58553872741703
1989	9.495221512630168
1990	20
1991	20.74074074074074
1992	21.875
1993	22.137404580152673
1994	23.809523809523807
1995	22.55639097744361
1996	24.615384615384617
1997	26.153846153846157
1998	26.24113475177305
1999	26
2000	29.927007299270077
2001	31.851851851851855
2002	30.82191780821918
2003	30.87248322147651
2004	29.629629629629626
2005	29.239766081871345
2006	28.49162011173184
2007	27.807486631016044
2008	28.04232804232804