Year	Percent
1965	25.69967
1966	26.38662
1967	23.62214
1968	22.75676
1969	23.56103
1970	22.01366
1971	22.97049
1972	23.0871
1973	24.46678
1974	26.30303
1975	25.54929
1976	25.14836
1977	24.1922
1978	23.36336
1979	25.10903
1980	23.51175
1981	25.38128
1982	19.99648
1983	20.2997
1984	21.03976
1985	21.61803
1986	21.77043
1987	22.27124
1988	23.5999
1989	23.70013
1990	21.38119
1991	19.411
1992	18.43945
1993	18.53526
1994	19.57703
1995	19.44225
1996	18.98981
1997	21.28826
1998	21.11811
1999	20.75551
2000	20.68334
2001	19.7409
2002	19.80963
2003	20.53914
2004	21.45588
2005	22.70463
2006	23.66495
2007	23.9706
2008	24.13246
2009	22.0151
2010	23.53731
2011	24.20796
2012	24.92753
2013	24.96959
2014	24.92764
2015	24.05761
2016	23.185
2017	23.69885