Year	% of total
1970	22.986242191670154
1971	25.60605940600482
1972	28.3988781675286
1973	32.13203543164764
1974	30.454303562295813
1975	24.787127093924493
1976	27.360413526559363
1977	26.529653006434984
1978	23.37351623042696
1979	23.046753344267064
1980	26.693055486896206
1981	20.064587740313222
1982	17.947339861720632
1983	14.72650950068433
1984	10.988106938588334
1985	10.111653829814744
1986	9.690697047572455
1987	9.009236637504081
1988	9.502660113912704
1989	9.08124963087125
1990	6.235565819861432
1991	6.181015452538632
1992	6.396588486140725
1993	7.079646017699115
1994	7.728337236533958
1995	8.951406649616368
1996	9.135802469135802
1997	8.837209302325581
1998	8.98876404494382
1999	9.395973154362416
2000	9.207708779443255
2001	9.355509355509357
2002	9.572301425661914
2003	9.722222222222223
2004	9.751434034416825
2005	10.515873015873016
2006	11.176470588235295
2007	11.363636363636363
2008	13.763440860215054