Year	% of total
1970	75.62786175792198
1971	75.81087566871108
1972	75.23243168973069
1973	75.19665061142416
1974	74.90803044020305
1975	75.41281306163955
1976	75.07313676193681
1977	74.61849679968907
1978	74.679228831426
1979	74.68015551070823
1980	74.31796127508102
1981	73.78779330428554
1982	73.6526177213052
1983	73.4362275937755
1984	73.2883123866969
1985	73.01259825141729
1986	71.87420301532138
1987	71.75188463451018
1988	71.27240997327331
1989	71.25807438631027
1990	78.37078651685393
1991	73.57075913776944
1992	70.1098901098901
1993	70.80820265379975
1994	74.64788732394366
1995	73.9294710327456
1996	70.25920873124147
1997	79.75708502024291
1998	78.92057026476579
1999	80.04179728317659
2000	79.72689075630252
2001	78.86266094420601
2002	79.48990435706695
2003	79.18410041841004
2004	77.80149413020277
2005	78.5643070787637
2006	78.60553963705826
2007	78.53211009174312
2008	78.68995633187772