Year	% of total
1970	8.876905289375925
1971	8.18479771748649
1972	8.329272464544621
1973	8.622954321636403
1974	8.101535843420846
1975	8.716898592307002
1976	9.295770848781387
1977	9.015019169210948
1978	8.828683359496418
1979	9.917438093958122
1980	9.315861578178948
1981	9.11300870481863
1982	9.05711161011324
1983	9.397358968871519
1984	10.332316870100849
1985	11.675951579104089
1986	13.530597470226283
1987	14.054379967486085
1988	14.284533484812753
1989	15.046888537702314
1990	10.472972972972974
1991	11.403508771929824
1992	11.551724137931034
1993	11.314475873544092
1994	11.73469387755102
1995	12.456140350877194
1996	12.136752136752136
1997	11.57167530224525
1998	11.32404181184669
1999	11.469534050179211
2000	10.200364298724955
2001	11.005692599620494
2002	10.982658959537572
2003	11.262135922330096
2004	11.368015414258188
2005	11.614173228346457
2006	11.928429423459244
2007	12.244897959183673
2008	12.007874015748031