Year	% of total
1970	75.1004027620163
1971	74.33110942812006
1972	74.50187029818588
1973	75.55041194868978
1974	76.77458438109662
1975	78.09919410100824
1976	79.75849572000617
1977	80.97735019484053
1978	81.84591081604408
1979	82.43551961444994
1980	83.19679163436507
1981	84.05889402496652
1982	84.80338826713646
1983	85.47806411865594
1984	85.88612685947481
1985	86.6653379453674
1986	87.219503493574
1987	87.4997291238888
1988	88.23433413755976
1989	88.41169267783793
1990	86.85590867016353
1991	86.02257636122178
1992	88.82220555138784
1993	86.10999598554797
1994	84.03324584426947
1995	84.26501035196688
1996	84.63962189838519
1997	86.80475642500959
1998	86.69340138534452
1999	85.96067609520524
2000	84.94132985658409
2001	85.10310864881502
2002	84.26512968299711
2003	83.36938885884263
2004	83.29907502569374
2005	82.20631132325643
2006	80.95238095238095
2007	81.0126582278481
2008	78.75662934590454