Year	% of total
1970	47.694204480077744
1971	54.003053069424546
1972	59.15689416423441
1973	60.93255088791335
1974	66.69119321726595
1975	59.22488695256432
1976	61.68728038082926
1977	56.360561907035645
1978	55.74631194284143
1979	63.24973325966009
1980	57.40642211987977
1981	50.41666521857204
1982	46.28103830023604
1983	45.973623534350736
1984	47.385937679830846
1985	48.11129190407105
1986	47.64965358682421
1987	45.3277129492715
1988	47.79904419743109
1989	48.34740966491672
1990	39.061671673440536
1991	37.705060324624604
1992	36.759131633356304
1993	35.75023458159174
1994	34.498951781970646
1995	36.59381663113007
1996	39.57164234942013
1997	42.57008429719662
1998	45.93730666116725
1999	50.065760631302055
2000	54.84589241767257
2001	56.09811492164434
2002	57.047274322693866
2003	57.62372058668355
2004	58.16222809514129
2005	58.19632259947466
2006	58.001155401502025
2007	58.248511618974455
2008	58.38432122370937