Year	% of total
1970	29.89735866146378
1971	29.81529846902044
1972	29.63457601488087
1973	29.88069022824933
1974	30.608902164573337
1975	30.117891766212573
1976	30.729631649052287
1977	28.194516308568364
1978	26.683212847990056
1979	26.22260553858714
1980	26.057079747721048
1981	26.51516111947499
1982	26.360274684910767
1983	27.688430046795627
1984	26.583296119158945
1985	25.329475408272284
1986	23.363856467202982
1987	23.0169770040355
1988	20.99032482672697
1989	21.017850741793577
1990	6.563706563706563
1991	6.172839506172839
1992	6.550218340611353
1993	6.103286384976526
1994	6.532663316582915
1995	7.027027027027027
1996	6.185567010309279
1997	6.763285024154589
1998	6.8807339449541285
1999	6.578947368421052
2000	5.9071729957805905
2001	5.737704918032787
2002	5.577689243027888
2003	5.769230769230769
2004	5.2434456928838955
2005	5.109489051094891
2006	5.536332179930796
2007	5.6105610561056105
2008	5.678233438485805