Year	% of total
1970	77.57305682105489
1971	77.44742393669806
1972	76.86363119646641
1973	76.90651132291507
1974	76.23111946231275
1975	75.31257756089273
1976	74.89808966685636
1977	74.86385091325839
1978	74.46290564233034
1979	74.36597617910775
1980	74.42206039484924
1981	73.87040510270604
1982	73.64944330427001
1983	73.81162309596377
1984	72.37991771631151
1985	72.2973780157558
1986	72.82427316965713
1987	71.98991146226675
1988	71.50940083085628
1989	71.91572198042786
1990	88.6178861788618
1991	85.88235294117646
1992	84.26966292134831
1993	79.05982905982906
1994	76.11336032388664
1995	75.19685039370079
1996	76.40845070422534
1997	77.57009345794393
1998	77.74480712166172
1999	77.52161383285303
2000	79.26136363636364
2001	78.24773413897282
2002	78.52760736196319
2003	79.57957957957959
2004	80.29850746268656
2005	81.00890207715133
2006	80.3680981595092
2007	81.73913043478261
2008	81.79190751445087