Year	% of total
1970	47.203098994092564
1971	50.82229944648172
1972	51.03934392784141
1973	52.71289509117529
1974	51.42953641753712
1975	51.90289636544547
1976	57.03953482495972
1977	52.319925981361706
1978	51.621723772918195
1979	40.224216854061595
1980	35.60733221500162
1981	30.011706887802976
1982	27.912441750629725
1983	26.34007640664763
1984	20.034345851279404
1985	18.465127684380757
1986	15.011325149070501
1987	13.01259688820414
1988	12.540680274695848
1989	11.655283055659105
1990	82.05128205128204
1991	80.83832335329342
1992	79.7752808988764
1993	79.14438502673798
1994	78.28282828282829
1995	80
1996	81.29770992366412
1997	82.53424657534246
1998	83.59133126934985
1999	84.22535211267605
2000	85.19480519480518
2001	84.98727735368958
2002	83.53808353808354
2003	83.17307692307693
2004	83.21513002364065
2005	82.67898383371825
2006	82.81938325991189
2007	82.98319327731093
2008	82.63473053892216