Year	% of total
1970	11.621288436234556
1971	20.485619980547927
1972	19.283665280347474
1973	18.097961437143802
1974	20.704037894326863
1975	17.994648377798946
1976	20.297440234910642
1977	17.914681568078123
1978	16.74362275725477
1979	13.043413882952626
1980	16.13064940834571
1981	18.839126851084224
1982	16.967783319103567
1983	17.03904846065087
1984	21.886187087698477
1985	21.465354899189016
1986	22.14582089211296
1987	16.331596517654667
1988	22.767663469132554
1989	20.178219938534127
1990	23.867924528301888
1991	20.582706766917294
1992	17.19626168224299
1993	13.92757660167131
1994	10.638297872340425
1995	10.825688073394495
1996	10.998151571164511
1997	11.701081612586037
1998	10.714285714285714
1999	11.100832562442182
2000	11.851126346718903
2001	11.775043936731107
2002	11.887550200803213
2003	12.818471337579618
2004	14.112903225806454
2005	13.823529411764707
2006	14.80916030534351
2007	14.440433212996389
2008	14.255910987482615