Year	% of total
1970	22.757521191685676
1971	22.530324134239503
1972	24.050258623381957
1973	24.197174993428106
1974	24.256840160301923
1975	24.805913106962876
1976	26.755129342961105
1977	27.920102692970033
1978	27.794063084983495
1979	27.260003026093386
1980	26.36472635246902
1981	25.4884844351484
1982	26.19221749422083
1983	26.151854016408222
1984	25.35294705061052
1985	28.05138060751135
1986	28.527824639994957
1987	28.81108623329957
1988	33.84685052236329
1989	36.55256077140185
1990	20.437956204379564
1991	19.799498746867165
1992	18.817204301075268
1993	19.83695652173913
1994	18.64406779661017
1995	19.710144927536234
1996	20.88235294117647
1997	20.178041543026705
1998	19.760479041916167
1999	18.93491124260355
2000	17.87878787878788
2001	18.639053254437872
2002	18.235294117647058
2003	19.08831908831909
2004	18.08219178082192
2005	18.784530386740332
2006	17.914438502673796
2007	17.46031746031746
2008	17.333333333333336