Year	% of total
1970	22.861690982847723
1971	22.472114371179636
1972	22.441608690660548
1973	22.82836368809751
1974	23.08547044887416
1975	22.519684885277144
1976	22.382477651753906
1977	21.909460538359905
1978	20.99582741717671
1979	19.828422047316014
1980	18.85075932754228
1981	17.99622595930678
1982	17.958654834598732
1983	18.108760768487397
1984	17.786152987504693
1985	17.77696305730656
1986	17.733493397390124
1987	17.26788591833619
1988	34.932818337386884
1989	34.97866934913909
1990	60.41923551171393
1991	57.67344078486335
1992	58.79354290569244
1993	55.61224489795919
1994	49.16467780429594
1995	41.07142857142857
1996	40.68027210884353
1997	40.921409214092144
1998	40.40816326530612
1999	39.620081411126186
2000	38.648648648648646
2001	29.329173166926676
2002	28.549141965678626
2003	31.90546528803545
2004	29.583975346687215
2005	24.382207578253706
2006	24.916943521594686
2007	24.829931972789115
2008	24.310344827586206