Year	% of total
1970	53.83529823842095
1971	53.350198569584116
1972	52.04816794691389
1973	50.03760048938627
1974	49.18431660942089
1975	49.61923083526864
1976	50.13710800665574
1977	50.488496803910046
1978	48.55205644964274
1979	49.32387212191606
1980	47.10400627870157
1981	45.9625985031172
1982	46.20882922336413
1983	45.463198422141225
1984	45.086398727664836
1985	44.56236712797336
1986	44.13196855306013
1987	43.17467660638977
1988	42.29179336514368
1989	39.295099439423964
1990	55.39748953974895
1991	53.23805270209915
1992	53.59195402298851
1993	55.181086519114686
1994	55.62098501070663
1995	55.89856670341786
1996	55.84632516703786
1997	55.694760820045566
1998	54.788816180844734
1999	52.73757079924481
2000	50.93209054593875
2001	49.42372881355932
2002	47.99154334038055
2003	47.801418439716315
2004	47.368421052631575
2005	49.039145907473305
2006	49.929971988795515
2007	48.37310195227766
2008	47.8448275862069