Year	% of total
1970	3.82564818780922
1971	3.7909525565292985
1972	3.7171494921994612
1973	3.7973110661775764
1974	3.751702156348579
1975	3.6380324001744304
1976	3.699457689267152
1977	3.607840326298527
1978	3.4857996910288236
1979	3.534734185431897
1980	2.5950352220588204
1981	2.312472067796991
1982	2.1671258686703827
1983	2.292515684989231
1984	2.5360745629728307
1985	2.5936688155331304
1986	2.4166007081857943
1987	2.4849743612130655
1988	2.5376406549624098
1989	2.541631516760274
1990	22.437137330754354
1991	19.73848069738481
1992	17.976115650534254
1993	15.449607724803863
1994	14.432328415651059
1995	11.29877693651718
1996	9.308966304968589
1997	7.710280373831775
1998	5.735377626348666
1999	3.959276018099547
2000	2.1715526601520088
2001	2.191341528594335
2002	2.1638330757341575
2003	2.169525731584258
2004	2.0972354623450906
2005	2.1634615384615383
2006	2.1626704278326283
2007	2.1809744779582365
2008	2.1257750221434897