Year	% of total
1970	80.18364758115666
1971	81.07948705191671
1972	81.09623992415705
1973	81.34139174389216
1974	81.23893514602129
1975	81.08987300352528
1976	80.71820269502012
1977	80.99460705370804
1978	80.77892079934603
1979	80.47457843281826
1980	80.80004065836147
1981	81.09718763938997
1982	81.48319954587467
1983	82.1890179805409
1984	81.9973200123351
1985	82.12355419668837
1986	82.0088981476737
1987	82.04395027910674
1988	79.9065289782918
1989	78.8307727733565
1990	87.61467889908256
1991	87.74509803921569
1992	88.0503144654088
1993	88.66666666666667
1994	89.65517241379311
1995	90.47619047619048
1996	90.71428571428571
1997	88.67924528301887
1998	86.66666666666667
1999	86.74698795180723
2000	87.34177215189874
2001	88.54166666666666
2002	87.35632183908046
2003	85.71428571428571
2004	85.39325842696628
2005	83.9080459770115
2006	84.33734939759037
2007	84.14634146341463
2008	84.33734939759037