Year	% of total
1970	79.72895918606507
1971	79.27163322357336
1972	79.46075080277598
1973	78.98998371883239
1974	78.66841405532934
1975	78.54145795559084
1976	78.35807431218737
1977	78.3685127452794
1978	78.1664712930915
1979	77.40880877684415
1980	75.7614366250295
1981	75.26195460882454
1982	74.71282984032916
1983	74.06271388467738
1984	73.79778610698942
1985	72.6788045098433
1986	73.78410296969598
1987	72.02600005946526
1988	71.42455887742139
1989	71.66421159917216
1990	86.0270078180526
1991	85.83786800613925
1992	85.57268722466961
1993	85.57114228456913
1994	85.37642885297596
1995	85.25138228108526
1996	85.33529845246868
1997	85.14839636189564
1998	84.98078938176738
1999	84.87727632620744
2000	84.5819881999332
2001	84.20417124039517
2002	84.07976114310087
2003	84.04781533388294
2004	83.90400642634803
2005	83.82625671059053
2006	84.42817932296431
2007	84.4081705467844
2008	84.65685435563923