Year	% of total
1970	83.57003110758265
1971	83.11509146648989
1972	83.41806941175895
1973	83.26053998268723
1974	83.96113742972894
1975	84.34356067016454
1976	83.62477301963784
1977	83.24866904715009
1978	82.40541360029536
1979	81.98172594742445
1980	82.3413955039572
1981	81.84606602034037
1982	81.91826218048504
1983	83.37418857074441
1984	82.1256204651271
1985	83.40651385539664
1986	82.71423277280074
1987	83.5729291987579
1988	83.60118775005839
1989	82.85708515399311
1990	81.08108108108108
1991	80.26315789473685
1992	79.48717948717949
1993	81.70731707317073
1994	81.3953488372093
1995	82.02247191011236
1996	80.89887640449437
1997	80.89887640449437
1998	80.68181818181817
1999	80.23255813953489
2000	79.3103448275862
2001	79.54545454545455
2002	78.82352941176471
2003	77.64705882352942
2004	76.74418604651163
2005	76.74418604651163
2006	77.64705882352942
2007	78.82352941176471
2008	78.57142857142857