Year	Percent
1965	30.29748
1966	29.32158
1967	35.24931
1968	30.83925
1969	29.66761
1970	22.52365
1971	25.89797
1972	24.88023
1973	23.62365
1974	18.48303
1975	19.98593
1976	19.86613
1977	17.80764
1978	21.76988
1979	19.25373
1980	22.0173
1981	21.42179
1982	21.6869
1983	21.25138
1984	21.58726
1985	17.70544
1986	21.19335
1987	24.11972
1988	24.90766
1989	24.59366
1990	25.31559
1991	27.05898
1992	23.53653
1993	23.71282
1994	22.43164
1995	20.9472
1996	19.54434
1997	21.13148
1998	23.34014
1999	23.182
2000	22.26529
2001	21.76412
2002	19.69386
2003	20.45694
2004	20.31605
2005	20.97179
2006	18.28431
2007	19.20872
2008	20.69288
2009	16.21202
2010	17.88551
2011	19.44597
2012	19.37318
2013	19.0174
2014	18.84644
2015	18.11858
2016	17.94545
2017	17.30403