Year	% of total
1970	55.330666607843995
1971	54.730285631036345
1972	53.69706272663495
1973	52.20943489782316
1974	52.10152127609956
1975	53.39042263201881
1976	53.67257807753536
1977	54.343640425753
1978	53.966201158928065
1979	53.81672344607925
1980	51.204764003381186
1981	51.325102928504016
1982	50.754522774773584
1983	48.26024863514627
1984	48.28612163352807
1985	44.03965779739363
1986	42.963324198426065
1987	44.023433228362805
1988	46.430467087377444
1989	47.248198968575224
1990	64.11960132890366
1991	64.44444444444444
1992	59.430604982206404
1993	60
1994	58.15899581589959
1995	58.44155844155844
1996	58.97435897435898
1997	63.19702602230484
1998	62.03703703703704
1999	58.36909871244635
2000	57.028112449799195
2001	58.44155844155844
2002	62.857142857142854
2003	62.12765957446808
2004	61.53846153846154
2005	60.71428571428571
2006	66.77966101694915
2007	65.91639871382637
2008	69.07514450867052