Year	% of total
1970	25.4926959404678
1971	24.743304210743368
1972	25.000511761701627
1973	26.133733649564867
1974	27.147547819754152
1975	28.150675515406586
1976	28.8325659338601
1977	29.419201411827583
1978	29.31164147954649
1979	29.8344395754819
1980	29.816549061379995
1981	23.94078576421202
1982	23.77519856312793
1983	23.836040312120797
1984	23.440367876655706
1985	23.676024854797586
1986	18.912960886732158
1987	19.378964258784436
1988	19.84344795407039
1989	19.883686975430113
1990	4.5602605863192185
1991	4.62962962962963
1992	4.143646408839778
1993	4.5584045584045585
1994	4.843304843304843
1995	5.056179775280898
1996	4.986149584487535
1997	5.053191489361701
1998	5
1999	4.922279792746114
2000	4.645476772616137
2001	4.600484261501211
2002	4.556354916067146
2003	4.513064133016627
2004	4.739336492890995
2005	4.694835680751173
2006	4.683840749414521
2007	4.62962962962963
2008	4.6082949308755765