Year	% of total
1970	71.47409407180629
1971	73.93483225206485
1972	71.14694498436576
1973	72.10078552917885
1974	72.5807791809173
1975	70.0843380884928
1976	69.16492994885155
1977	71.343396926367
1978	69.65567208624964
1979	68.76375429991427
1980	67.630057532379
1981	69.02245858223073
1982	67.8715606151171
1983	67.80512881707162
1984	70.71797623565126
1985	70.68305010736866
1986	70.42809951913026
1987	70.25023900804418
1988	71.92316829145679
1989	72.44443389358402
1990	86.71096345514951
1991	86.20102214650767
1992	85.91065292096219
1993	86.40132669983416
1994	82.27272727272728
1995	83.33333333333334
1996	83.61344537815127
1997	83.88429752066115
1998	84.15446071904128
1999	84.76312419974393
2000	85.16687268232386
2001	85.29048207663782
2002	85.76598311218335
2003	85.78255675029868
2004	85.93563766388557
2005	86.07142857142858
2006	86.14668218859138
2007	86.54060066740823
2008	86.07021517553794