Year	% of total
1970	61.71380294991441
1971	64.81123041290012
1972	62.644448145134604
1973	66.7517067409115
1974	68.47364381965144
1975	62.0548512573521
1976	59.828766677791414
1977	58.35810942110336
1978	66.84606650365996
1979	66.04798858587174
1980	65.94762614876181
1981	68.67809170292692
1982	60.71329869772403
1983	62.97552541163191
1984	62.12467218146901
1985	63.37987390792489
1986	62.986258266119876
1987	58.968128923967015
1988	56.74858939182633
1989	57.84391342267118
1990	70.76612903225806
1991	72.72727272727273
1992	75.79617834394905
1993	78.95878524945769
1994	80.66037735849056
1995	79.8076923076923
1996	79.85948477751757
1997	78.55421686746989
1998	80.50847457627118
1999	79.78494623655914
2000	48.78378378378378
2001	49.86772486772487
2002	48.30393487109905
2003	49.80289093298292
2004	53.62318840579711
2005	49.73890339425587
2006	52.05992509363296
2007	52.18476903870163
2008	50.25974025974026