Year	% of total
1970	7.937705647404117
1971	8.193494612413684
1972	10.682461525922877
1973	12.790689115396908
1974	13.741929564976434
1975	13.523161586739882
1976	12.570142365301953
1977	13.922921057168411
1978	12.804657122404816
1979	12.113643295174628
1980	12.80310809220222
1981	12.43183737829625
1982	12.847380917497963
1983	13.965052273905071
1984	14.243302560507528
1985	12.53639120855952
1986	11.144491113350131
1987	10.561699802784837
1988	11.062830148286123
1989	10.634448003118525
1990	3.3816425120772946
1991	3.3175355450236967
1992	3.255813953488372
1993	3.1963470319634704
1994	3.153153153153153
1995	3.1390134529147984
1996	3.125
1997	3.5555555555555554
1998	3.5398230088495577
1999	3.524229074889868
2000	3.508771929824561
2001	3.508771929824561
2002	3.0837004405286343
2003	3.0837004405286343
2004	2.643171806167401
2005	2.643171806167401
2006	2.643171806167401
2007	2.2026431718061676
2008	2.1929824561403506