Year	% of total
1970	7.454417398181485
1971	7.4301587889766205
1972	7.440811017324708
1973	7.440616548881808
1974	7.486950865019875
1975	7.825211824148962
1976	7.734023950274834
1977	8.082911586934506
1978	8.264767479222083
1979	8.407596023468008
1980	7.851962559021447
1981	7.864373412980179
1982	8.12687381649794
1983	8.052231608284737
1984	8.413614926662662
1985	8.36314309033793
1986	8.35159079777039
1987	8.371220014858075
1988	8.433210076126414
1989	8.17540734688969
1990	16.27906976744186
1991	15.789473684210526
1992	16.05839416058394
1993	18.253968253968253
1994	18.6046511627907
1995	18.939393939393938
1996	19.852941176470587
1997	21.58273381294964
1998	22.69503546099291
1999	24.647887323943664
2000	25.694444444444443
2001	27.33812949640288
2002	27.464788732394368
2003	26.845637583892618
2004	27.333333333333332
2005	27.450980392156865
2006	26.71232876712329
2007	24.489795918367346
2008	22.916666666666664