Year	% of total
1970	64.2919989912514
1971	64.54778802742386
1972	64.21741009633554
1973	64.42679408376848
1974	65.1701110599734
1975	63.74438705279765
1976	63.0150666757307
1977	61.54134655578199
1978	61.08047311582771
1979	60.38976943960991
1980	61.0995289787222
1981	59.41638076241921
1982	58.10940307177869
1983	56.19691105075933
1984	55.21265735294255
1985	53.87709284353338
1986	52.647951234820276
1987	52.4477225115949
1988	51.39605475990291
1989	50.73720005414384
1990	56.993006993006986
1991	56.272401433691755
1992	51.574803149606296
1993	52.362204724409445
1994	51.6
1995	51.19047619047619
1996	51.96850393700787
1997	50
1998	49.2
1999	47.28033472803347
2000	47.5206611570248
2001	48.582995951417004
2002	47.17741935483871
2003	46.82539682539682
2004	45.52845528455284
2005	45.867768595041326
2006	45.79831932773109
2007	46.58119658119658
2008	48.917748917748916