Year	% of total
1970	46.1338011699496
1971	44.207124849180566
1972	45.98857395190591
1973	46.05096659449428
1974	45.287692934322735
1975	44.27317146070375
1976	46.592383415628184
1977	44.300156830752016
1978	45.9154223058457
1979	48.82448103096056
1980	48.76984794277698
1981	50.98786773406256
1982	51.4775520374039
1983	50.5681734827536
1984	51.280018172377986
1985	49.75673985693657
1986	50.436995030448
1987	50.83167668659908
1988	41.700476866318816
1989	60.011498691301
1990	71.39451728247914
1991	76.05042016806722
1992	71.50943396226414
1993	69.58424507658644
1994	69.04761904761905
1995	57.30593607305936
1996	57.36607142857143
1997	63.24582338902148
1998	68.05555555555556
1999	69.64285714285714
2000	65.95744680851064
2001	67.67676767676768
2002	73.97260273972603
2003	73.88392857142857
2004	70.0228832951945
2005	65.6641604010025
2006	69.93865030674846
2007	70.1657458563536
2008	72.63157894736842