Year	% of total
1970	69.18267414133258
1971	68.51898450634269
1972	66.70291597165108
1973	65.45685451996813
1974	63.47758810875338
1975	64.12594941706068
1976	64.95723678067462
1977	65.8911104654608
1978	65.07357067050546
1979	66.35330818253463
1980	67.89250511704368
1981	66.91664612994043
1982	68.23264442312323
1983	67.55943527106973
1984	67.43881011306705
1985	69.12140203200691
1986	69.19922795356678
1987	69.3560772933172
1988	69.13054989123859
1989	69.57876964684358
1990	87.34177215189874
1991	87.44884038199181
1992	87.36702127659575
1993	87.35332464146023
1994	87.29351969504448
1995	87.422934648582
1996	87.87128712871286
1997	88.71548619447779
1998	89.20863309352518
1999	89.92890995260665
2000	90.94972067039106
2001	89.86175115207374
2002	89.50276243093923
2003	90.81908190819082
2004	90.49694856146469
2005	90.18612521150592
2006	89.62585034013605
2007	89.37759336099586
2008	89.23694779116465