Year	% of total
1970	79.4274020365478
1971	78.25417632721003
1972	79.0420871061756
1973	78.76375416693287
1974	77.28775207121042
1975	75.18317555012764
1976	74.67300429069354
1977	74.74606033162094
1978	74.78697412124059
1979	74.18967443984567
1980	76.34665708558678
1981	76.1701614638721
1982	75.17598751990816
1983	76.37763932156454
1984	76.51646343217048
1985	76.42967068842165
1986	77.09351603352091
1987	75.82138919086815
1988	74.87269390330165
1989	76.47085587631123
1990	78.3132530120482
1991	78.8679245283019
1992	79.49640287769785
1993	79.7945205479452
1994	79.18088737201366
1995	79.19463087248322
1996	77.7027027027027
1997	77.63157894736842
1998	76.41196013289037
1999	77.01863354037268
2000	76.82926829268293
2001	76.8545994065282
2002	76.03550295857988
2003	77.17391304347827
2004	77.12765957446808
2005	77.83375314861462
2006	77.46835443037975
2007	77.64127764127764
2008	75.59055118110236