Year	% of total
1970	79.75075511080676
1971	79.1733894098105
1972	78.85676789086385
1973	78.53359120830193
1974	77.6764335113163
1975	77.7127756469346
1976	78.3924394006735
1977	78.03765439389323
1978	77.42897192518724
1979	76.25858140389562
1980	76.3760006378568
1981	77.40073427093635
1982	75.64795311620625
1983	77.32740710570306
1984	76.98877965657361
1985	76.78015648462815
1986	75.98950802941154
1987	70.23469754734208
1988	68.49199906760566
1989	68.76665127880058
1990	91.27222982216142
1991	90.43453724604966
1992	91.0935738444194
1993	90.85094549499443
1994	90.57388411422235
1995	89.22121896162528
1996	88.6954118297402
1997	89.09242298084929
1998	89.43699731903484
1999	89.45205479452055
2000	90.17467248908298
2001	90.2860226659471
2002	89.78760546988653
2003	89.8567335243553
2004	89.59288990825688
2005	89.98375744450459
2006	89.52618453865337
2007	89.55465587044534
2008	89.25802879291251