Year	% of total
1970	33.61241686083457
1971	34.721471661158034
1972	35.290453747049334
1973	35.395082188954355
1974	35.59904227731428
1975	37.186531676797095
1976	37.2535773676739
1977	38.03698748918911
1978	38.607752242405965
1979	38.97411577366961
1980	40.48765212761912
1981	40.79346119264237
1982	42.0544306198256
1983	43.61287741648884
1984	44.19965994154131
1985	45.54429928684057
1986	46.914120656628114
1987	47.82499415412155
1988	48.30528542646073
1989	47.61739484821569
1990	66.39344262295081
1991	67.85714285714286
1992	70.55837563451777
1993	71.6867469879518
1994	73.18840579710145
1995	78.29457364341084
1996	74.82014388489209
1997	73.15436241610739
1998	70.3225806451613
1999	70.41420118343196
2000	68.92655367231639
2001	74.35897435897436
2002	74.35897435897436
2003	73.8562091503268
2004	67.26190476190477
2005	65.4054054054054
2006	60.55555555555555
2007	57.14285714285714
2008	53.75722543352601