Year	Percent
1965	17.53771
1966	16.94963
1967	14.64584
1968	13.19081
1969	14.2101
1970	14.18389
1971	13.79161
1972	13.34848
1973	13.98208
1974	20.51164
1975	20.18015
1976	22.26847
1977	22.48322
1978	21.74579
1979	29.72845
1980	30.51464
1981	33.37182
1982	27.03431
1983	25.482
1984	22.35125
1985	19.91428
1986	15.73157
1987	12.55871
1988	17.31839
1989	17.89348
1990	20.0476
1991	27.8156
1992	28.39684
1993	25.83763
1994	22.57143
1995	22.54902
1996	20.74978
1997	18.84167
1998	16.21434
1999	15.05202
2000	16.20112
2001	17.47979
2002	18.31618
2003	21.79641
2004	28.22996
2005	30.34355
2006	29.94981
2007	30.24973
2008	33.04299
2009	24.95682
2010	21.34925
2011	20.56743
2012	16.39697
2013	17.01785
2014	14.24413
2015	13.18385
2016	10.34546
2017	16.29971