Year	% of total
1970	49.850719351813524
1971	49.457752745366975
1972	49.67055505605557
1973	49.77646662804291
1974	49.62372904086138
1975	50.028018768682195
1976	48.550441595525335
1977	47.47276243846873
1978	46.073785201646004
1979	45.56125294866115
1980	43.09125477570814
1981	40.81837852204973
1982	40.21560703303076
1983	39.84951571791815
1984	37.596436078922046
1985	35.35563818460876
1986	34.98878280382716
1987	35.38253874416846
1988	34.89389205401829
1989	35.66039901365526
1990	39.80669813441223
1991	39.57089139570891
1992	38.80957610366791
1993	37.5686964167949
1994	36.55701754385965
1995	38.05289557683538
1996	40.58616647127784
1997	42.846715328467155
1998	45.47972802820448
1999	47.4814422057264
2000	49.72035794183445
2001	51.14571092831962
2002	47.43486435670158
2003	45.20255863539446
2004	43.641618497109825
2005	43.75629405840886
2006	41.94605495336526
2007	41.882640586797066
2008	41.28352490421456