Year	% of total
1970	83.07558764957807
1971	83.12855994430844
1972	82.15627421863225
1973	82.97953019217067
1974	82.16317243383648
1975	83.06665019562388
1976	82.30167820901634
1977	82.332945544088
1978	82.03174582697889
1979	80.95621196760735
1980	80.94238377754517
1981	80.80222490447066
1982	80.30811967194244
1983	81.90337972477441
1984	81.17604409368542
1985	80.02375675469885
1986	78.1041703150398
1987	76.6913604823427
1988	76.58757124154884
1989	74.90277174361228
1990	89.40432261465472
1991	89.23024983119514
1992	88.87785501489573
1993	88.3217707300958
1994	87.82608695652175
1995	84.15458937198068
1996	80.76259218578377
1997	78.25185185185185
1998	74.38622754491018
1999	72.10398514497929
2000	69.35956467141064
2001	68.9274017467249
2002	67.51136207134003
2003	67.8820587073845
2004	67.11470703379877
2005	66.98807409286984
2006	66.35338345864662
2007	66.83844678811121
2008	66.18815992407166