Year	% of total
1970	81.31657464742061
1971	81.50779503965632
1972	81.50669074009677
1973	81.46735688837121
1974	81.5716043401019
1975	81.50233148881604
1976	81.83118253659042
1977	81.69909982164253
1978	81.70418603619918
1979	81.49413012362292
1980	81.58012454671773
1981	81.78473865502696
1982	81.71571486611516
1983	81.62351308899628
1984	81.28856856739458
1985	81.43761733671028
1986	81.85349921117873
1987	81.65204521868534
1988	82.01194522960866
1989	81.85861686188638
1990	81.52562574493444
1991	81.51210868281157
1992	81.3599062133646
1993	81.23543123543124
1994	80.98837209302326
1995	82.19552157291098
1996	80.97982708933718
1997	80.6581986143187
1998	81.79871520342613
1999	81.93717277486911
2000	80.32694475760992
2001	79.79359043997827
2002	80.55281342546891
2003	81.34529147982063
2004	79.97262773722628
2005	79.98266897746967
2006	78.04085422469824
2007	78.97702644126572
2008	78.71244635193133