Year	% of total
1970	77.32365807280291
1971	76.69958187648687
1972	76.00726925398374
1973	77.7258458063023
1974	78.66662249691781
1975	79.1823607362898
1976	78.83933190393259
1977	79.73548324925639
1978	79.08813563861898
1979	78.5599628528
1980	80.37129901780425
1981	81.17124960995994
1982	82.4012269646828
1983	81.5803161817805
1984	81.70065196912074
1985	81.72548504998672
1986	81.27239567497516
1987	80.75182889226285
1988	79.91490432183672
1989	78.85958013844427
1990	5.194805194805195
1991	5.128205128205128
1992	5.128205128205128
1993	5.128205128205128
1994	5.063291139240507
1995	5.063291139240507
1996	4.938271604938271
1997	4.938271604938271
1998	4.878048780487805
1999	6.024096385542169
2000	6.024096385542169
2001	5.813953488372093
2002	5.617977528089887
2003	6.593406593406594
2004	6.382978723404255
2005	7.291666666666667
2006	7.000000000000001
2007	6.730769230769231
2008	6.5420560747663545